First off let me say, there are a lot of ways to play and build Malphite, this is a full guide to him, not a build. Read the whole thing before you judge. Malphite is my favorite champion and one of the most versatile in the game. Enjoy!

AP=Ability Power
AD=Attack Damage
AS=Attack Speed
MR=Magic Resistance
HP=Health Points
Ult=Ultimate Ability
CC=Crowd Control(Slows, Stuns, Silences, Etc.)
DPS=Damage Per Second

Tank

Probably Malphite's best role, although it is not what riot claims for him, Malphite is one of the few champions in the game to naturally scale armor and magic resistance. His passive also makes him extremely hard to harass early and even late game can take an entire ability from an AP caster.

AD Off Tank Bruiser

This is also a very viable role for Malphite, his natural tankiness makes it very easy to take it just a little farther and the active on his can easy give him extreme damage. Quite possible the most fun way to play Malphite.

Jungler

In my opinion Malphite is one of the best junglers in the game. Although he does not get through his jungle very fast he does it with very high hp, this plus his makes him very hard to gank. Also since he already has a long slow he is capable of ganking without red buff at level 3. Once he hits 6 however he has one of the strongest ganks in the game, able to use his ult from the bushes, even a full hp champion is almost guaranteed to die.

AP Off Tank

This is Malphite's least used and worst role. Not to say it isn't viable however, he gets a 1 ratio on his Ult and a .6 ratio on his Q. Although he does need some tankiness to him Malphite can easily be built to the point of nuking squishies from full hp to death in the matter of a second or so.

Honestly, anywhere, I have found success in all 3 lanes and the jungle with Malphite. It really depends on your team comp. Preferably he is top solo but if you have a Garen or a Nasus and they want it then let them have it. If you don't have a proper AP carry, or they are not comfortable going mid, say you have Annie and they have Talon, then go mid. If you don't have a proper support then go bottom and protect your AD carry. If you are last pick and need a tank and a jungler and Amumu is banned, go for Malphite. This is why Malphite is so versatile.

Pros

+Very strong early game
+Very versatile
+Has an unexpected nuke
+Can be built into perhaps the toughest tank in the game
+Hard to harass early game
+Has plenty of CC

Cons

-Mana hungry
-Can't 1v1 bruisers late game
-Fairly difficult to use Ult properly
-Doesn't look as badass in game as my picture above

Granite Shield

-Malphite is shielded by a layer of rock which absorbs damage up to 10% of his maximum Health. If Malphite has not been hit for 10 seconds, this effect recharges.

This passive is what makes Malphite truly unique, no other champion has a passive like this and him makes him nearly unharassable in the lane early game. Many people think this is why he should stack health however if you are reading this you probably already know that HP tanks are the weakest kinda and that Malphite would benefit much more from armor anyways.

Seismic Shard

-Using his primal elemental magic, Malphite sends a shard of the earth through the ground at his foe, dealing damage upon impact and stealing movement speed for 4 seconds.
Deals 70/120/170/220/270 (+0.6) magic damage and steals 14/17/20/23/26% Movement Speed from the target for 4/4/4/4/4 seconds.
Cost
70/75/80/85/90 Mana
Range
625

This is Malphite's best ability, even better than his ult in my opinion. The movement speed steal is huge for early game harrasment and the damage is awesome. This ability makes it just about impossible to get away from Malphite without using some sort of distance covering ability such as .

Brutal Srikes

-Malphite hits with such excessive force he deals damage to units around his target. He can also call upon his strength to increase the damage he does for a short time.
Passive: Malphite's basic attacks hit units near his target for 30/38/46/54/62% of his Attack Damage.

Active: Malphite's Armor and Attack Damage increase by 20/25/30/35/40% for 6/6/6/6/6 seconds.
Cost
55/60/65/70/75 Mana
Range
400

This is the ability that makes him a viable off tank DPS and jungler. The passive makes him really great for pushing minions and the active gives him extreme damage and armor. Also it adds a cool skin effect to him that makes him look molten, pretty sweet.

Ground Slam

-Malphite slams the ground sending out a shockwave that deals base damage plus half his armor as damage and reduces the attack speed of enemies for 4 seconds.
Malphite slams the ground dealing 60/100/140/180/220 (+) magic damage to surrounding enemies, reducing their Attack Speed by 30/35/40/45/50% for 4/4/4/4/4 seconds.

This ability gains damage equal to 50/50/50/50/50% of Armor.
Cost
60/65/70/75/80 Mana
Range
350
This ability is the perfect for AD champs and early game lane fights. It has good damage and a huge AS debuff. In a team fight this paired with your ult can make an AD champ useless. In lane fighting where someone might think they can get in a basic attack fight with you after a few hits they realize that they aren't doing any damage.

Unstoppable Force

-Malphite ferociously charges to a location, damaging enemies and knocking them into the air.
Malphite charges toward the target area, dealing 200/300/400 (+1) magic damage and knocking enemies into the air for 1.5/1.5/1.5 seconds.
Cost
100/100/100 Mana
Range
1000
Although this ult if fairly low damage it can hit their entire team and the knock up is a huge team fight winner. This may very well be the best initiation in the game, especially because fully comboed can do easily 1000 damage total to a carry, which basically means 1 second into the fight nearly dead carry.

1)The first is that the 4% damage reduction for going full 21 points in defense is not very much (40 HP per 1000:()
2) Second is putting points in is basically useless
3)I put points in because Malphite is mana hungry this helps alot more than you would think
4) I put 3 points in because lets face it, movespeed is always awesome.

Flash

-Flash is just by far the best summoner spell.It can be used to chase and escape, 80% of people use it, why not for Malphite.

Ignite

-Sometimes you just need that little bit more damage, ignite is the answer.

Ghost

-Basically same reason as flash but you can also use it to gank and defend towers, really just a matter of play style.

Clarity

-Mana is an issue for Malphite, however with proper management you shouldn't need this, but hey it works

Teleport

-Map movement is made easy with teleport, never a bad choice

Heal

-Really jsut depends on your play style, sometimes heal is a good choice, especially for newer players

Exhaust

-Great for early lane kills, usually the job of your melee dps, such as Xin Zhao, but still viable.

Cleanse

-With and you should have no problem getting out of CC. Besides you are a tank, taking damage and baiting CC is your job. Don't give the enemy a reason to no dump CC on you. I just can't justify using this over any of the suggested spells above.

Fortify

-You have no way to get people into turret fire, don't use this spell.

Rally

-Rally is aweful, just never use it.

Revive

-Not even going to explain, do you plan on dying?

I think that this is a very important point that most people do not understand, or maybe understand conceptually but do not know the numbers I would like to clear that up. The equation for damage taken for armor and mr is this 100/100+armor or mr. Lets do some simple calculations:
50=100/100+50=66.67% damage taken
100=100/100+100=50% damage taken
200=100/100+200=33.33% damage taken

As you can see, stacking armor and mr can really help, ALOT. However you can see that it gives diminishing returns. But coupling resistance and health is the most efficient. More calculations

Lets say you currently have 100 in both armor and mr with 2500 hp, and you have a choice buy more resistance or buy hp, say a or a , which will do more?
100/100+100=50% which means your effective hp is 5000 (1/.5 x 2500)
=100/100+100=50% effective hp is 7860 (1/.5 x 3930)
=100/100+200=33.3% effective hp is 7508 (1/.333 x 2500)

Now although the effective hp is higher with the we have to look at the added benefits from and the fact that it doesn't take 20 minutes to build. So like I said, in terms of allowable damage, the combo is better, but in terms of your job as a tank, taking items that offer your team or yourself more utility will most likely be better.

The first major reason I would say that resistance is better than hp is for tank shredding. Since the hp tank is the most obvious and simple form there are many abilities and items that aim to counter this, things like and . These items tear up hp tanks but the %life is not true damage and can be mitigated.

The final thing to consider when thinking armor or mr is the point value for effective damage of each health point, in our experiment above the first champion has an effective damage of .4 whereas the second has an effective damge of .28. This means that the second champion will benefit more from hp regen because each point regenerated will give him essentially more back, this means that during and after a team fight the second tank will have more sustainability from his awesome regen. Using another example, for a mana hungry champ, like Swain that rushes a you don't start with a you start with a . Although you will have more mana to start, you will burn through it and then be left with nothing, however if you are regenerating your mana you will always be lower but never run out, same goes for a tank. Many times I have gotten extremely low in a fight backed off, waited for my shield to come up and then went back in, just waiting 10 sec, I essentially reclaimed about 20% of my health and am basically ready to fight again. Not to mention when using a , you get up with the same health regardless of your max hp, so why not put it to the best use possible, food for thought.

Okay so I am sure many of you just read the item section and saw on my Tanky DPS build that I build but I do not build a . I'm sure your saying wow this guy doesn't understand what Atmog's is, lol. Not true, I just think that for the rest of the build, doesn't add much, although fully stacked it adds a whopping 1430 hp, still add's 700, meaning at best is only 730 hp more, meaning only 14 more points of damage, add's 20 and an awesome slow, it is Tanky DPS, not tank. Besides look at the rest of the build, every item adds health.

Talon

-Talon's passive needs CC, your Q is spammable and the effect is long, really good lane mate

Caitlyn

-Caitlyn has great range and anyone with a slow can allow her to get in alot of auto attacks, your ult garantee's her peacemaker and the knock up is long enough for her trap to settle witch grants a 4 second stun/snare

Nunu

-His ult sinergizes with yours, get people baited into the bush he can start his ult then you ult, 2 easy kills, plus between his and your Q they are perma slowed.

FiddleSticks

-Again your ult plus his are a match made in heaven. Also your Q will allow his drain to be much more effective.

Xin Zhao

-Xin's knock up requires him to get three hits, your slow allows that too happen, his massive damage is complimented by your debuff's.

Sona

-A support champ that can deal damage and keep you healed. As a bruiser getting in hits is important, heals help you do that. And together your ults make over 3 seconds of suppression for the enemy.

Nasus

-The only champ that can out debuff you on AS and Movement Speed, with his wither. Try not to get in an auto attack fight with him unless he was recently used this ability.

Vayne

-She is a tank slayer, silver bolts will mess you up, early game she isn't that big of a threat however

Vladimir

-His transfusion outranges your Q and he can use his blood pool to avoid damage and heal himself, a real pain in the ***

Kassadin

-His silence will outrange your Q and he can rift walk to dodge your ult, very hard to lane against but not enough burst to be a real problem late game.

Cho'Gath

-He has more sustain than you do in lane. His silence plus rupture can really swing the tide of a fight.

Yorick

-All of his ghouls can really make fighting him challenging. Keep your distance until you see an opportunity that he is on cool down and you can get in a few good hits. One of your most challenging top solo opponents.

Annie

-Annie does not outrange your abilites. Her main harass is Q and W which will get your shield down plus like 50 damage early game. If you see her stun up be aggressive, she will always go for the combo and will run herself out of mana. She is extremely squishy and can be bursted down with ease. I recommend going mid if she is mid and your AP carry is not a good counter to her.

Teemo

-Teemo is extremely squishy and you don't need basic attacks to get him low so his blind is basically only good for its damage which is not good.

Irelia

-She has a stun but it is short, even if she dashes and stuns you before she gets away you can Q, E her. You will win basic attack fights against her, especially with your W activated. One of the easiest typical top solo's you can be matched against.

Mordekaiser

-Although he has a shield you do too, if you can get your Q off first you can easily run up and use E to put his shield all of the way down. At this point he has hurt himself 50 points for basically no shield, with your AS debuff you will win in a basic attack fight. It is easy to bait him into fighting and you will almost always win.

There are many ways to play and build Malphite, I suggest tank because it is his strongest role. Malphite's damage will surprise most players, have fun with him and I hope this guide was useful. Thanks please upvote!