So a lot of people think Malphite is a weaker champ than he is. They tend to underestimate just how well he can do if he is built right. Some build him straight health, straight armor/magic resist, or straight attack damage. All of these, in my opinion, are mistakes. People just focus way too much on a singular aspect of him. Sure, it's fun to try, but realistically- is 10000+ health and 280 health regen/5 REALLY necessary? (And yes, I have seen someone try it-6 warmogs). Or maybe 680 armor? Perhaps 450 attack? But in the end, you either die too quickly to even help in a fight, or you don't do enough damage to help even if you are indestructible. So, the aim of this guide is to build the balanced Malphite- either tank or bruiser, you're gonna end up with 3500+ health and A LOT of health regen, and hopefully that feeling of "Yea, I'm awesome" when you score double kills every other minute.

Pros:

-Starts off tanky
-Decent damage with armor scale
-KICK-*** Passive!
-W's passive=farm-o-matic
-Harass with combo is fantastic

Cons:

-Slow early game
-Mana dependent (though not a problem in this build)
-Ult can leave him very vulnerable
-Combo harass is mana expensive early game

Alright, so first we've got what I call the "Super Tank".
For marks, I stack Greater Mark of Armor all the way. The reason is fairly self explanatory, starting the game off with an additional instant 7 armor.
For seals, the stack is again full armor, with [[Greater Seal of Resilience]x9] for an additional 13 armor to start the game.
Glyphs are where the balancing begins. First, you'll want 5 Greater Glyph of Magic Resist to grant some extra magic resist against any early game casters. The rest of the glyphs should be 4 Greater Glyph of Replenishment. The reason for this is that although glyphs are not the best for mana regen, they are enough to bring your unassisted mana regen in early game to about five, with your quints.
Quintessences are simply 3 Greater Quintessence of Replenishment. These are a godsend early game, in addition to your glyphs, as they allow you to harass and sustain much longer in lane, and in teamfights.

The second build here is the bruiser build.
Starting with marks, we have a full set of Greater Mark of Desolation for an additional 15 armor penetration without any items! This makes your early game attacks penetrate half of their starting armor, upping your damage a lot.
On to seals, we have a fully stacked set of 9 Greater Seal of Replenishment, for a starting mana regen of 4 per 5, so that you once again have some decent mana regen in the beginning of the game.
For glyphs, we again want 4 Greater Glyph of Replenishment to bring your mana regen up to 5 per 5 for the start of the game. The other 5 should be Greater Glyph of Magic Resist to boost your magic resist up a bit, so you're not magic-vulnerable early game.
For quintessences on this build, we stack another 10 armor penetration with Greater Quintessence of Desolation, so that your total unassisted armor pen is 25! This means you're dealing practically true damage to anyone early game without an armor item or runes/masteries.

For Summoner Spells, Teleport and Garrison are the best fit for the "Super Tank" playstyle. Teleport is a perfect fit for Malphite, as it allows early game mobility between your pool and your lane, and serves late game as both a valuable ganking tool and a way to get back into a teamfight fast, since your team is gonna need you. A lot. Garrison is great from protecting your inhibitors to preventing their AD carry from eating your towers for dessert. Popping Garrison and a quick ult could very well land you a kill and, if your team follows up, some assists.

If your going for the bruiser option, Teleport is still one of the most viable options. It has the same uses, but you have to rely on your damage to take care of any enemies, not Garrison. For this reason, Ghost is the number one pick on the bruiser build. It allows for chasing and escaping, and helps if you over-initiate or extend. This is also why the second pick for this build is a definitive combat spell. Flash is my personal pick, as it is the best spell for finishing off low health enemies, or escaping should you find yourself being a failwhale. (Again, shouldn't happen often, just play smart) These two together make you extremely mobile.

Alternates that I would consider would be something like Exhaust on the bruiser in place of Flash, which isn't quite the same effect on chasing and escaping, but maybe more useful in close fights.
On Super Tank, I wouldn't change anything really, but if you were going to be a more offensive tank, then switching out Garrisonfor Cleanse might be beneficial if you find yourself getting focused down too often.

Pretty self explantory, Malph should be 0/21/9 almost all of the time. If you are going the bruiser path, I might consider going 21/0/9 or 21/9/0, but only in the event that you are actually building more attack damage than bruiser, which I don't recommend, but that's your judgement call. Anything that looks like x/x/21 isn't recommended, unless your going uber support tank, in which case this probably isn't your guide.

*Malph needs to be tanky to get his skill combo down entirely. Add in a few good attacks, and you're good. If he's not, once his ult goes down, he tends to get dropped like third-grade French.

*Also, added in the JunglePhite and AD Malphite builds-in testing, so no new data yet!

Items should be self explanatory for the Super Tank. Of course, substitutions can happen, like a Thornmail or Randuin's Omen for the Force of Nature on an AD heavy team. Bootwise, the only change that would be a possibility for me is Mercury's Treads instead of Ninja Tabi, but only against those uber-CC teams- the dodge helps in fights, and procs more often than you'd think (the armor doesn't hurt either). Spirit Visage is on there for the little bit of extra health, and the sweet buff to health regen that boosts your Force of Nature and Warmog's Armor regen effects. Otherwise, this build is solid against any average-built team.

For bruiser, it should also be straightforward, but some people think some of these choices are questionable. Starting with boots, Berserker's Greaves over Ninja Tabi is something a lot of people have told me they disagree with. Well, if you want to revert to Ninja Tabi, that's your choice- on the bruiser I tend to want that extra attack speed, as it helps your farming a bit, and makes you more lethal against people that would normally get away with what seems to be just enough health to survive every time.

For other items that aren't so bruiser-ish, they are there simply to give you the survivability you need as Malphite, and to get your passive up as much as possible. To couple this with attack damage, the build includes Frozen Mallet to boost your effectiveness a **** TON in fights. The straight survivability is strictly from Warmog's Armor and Thornmail, which are really there to boost your health and armor to insane amounts. Sunfire Aegis is still on this build because of the kick-*** passive it procs constantly, making farming so easy, you'll actually sicken yourself.
Lastly, we have Trinity Force and Atma's Impaler. These two make your attack damage become a threat. Atma's Impaler adds more armor to your build, which always helps, and it adds a decent amount of damage because of all of your health. This is added to again when you complete your Trinity Force, as well as the little bit of extra damage your Seismic Shard and Unstoppable Force gain from the AP, and the proc on your next attack from the Sheen effect.

So I chose, like most others, to max Seismic Shard first. It offers alot of utility, being both a slow and a speed boost, since you're actually stealing movement speed. On top of this, it is your only target-specific ability, and gains damage fairly quickly, so harassing is a breeze as long as you watch your mana. This is the same between both builds.
For your other abilities, the builds differ slightly. For the "Super Tank", you're gonna want Ground Slam maxed out next. This is because you'll have much more armor in that build, making the damage scale on Ground Slam begin to skyrocket, on top of the amazing attack speed slow on enemies. This will make team fights slow down for a second, giving your team time to get some damage out.
This makes your last priority Brutal Strikes. The reason for this is that you don't need the damage boost that badly, and your other abilities are more useful throughout the game. However, I do grab one point in Brutal Strikes early game for the farming capabilities and for the armor boost its active gives you, offering survivability and (what most people forget) an armor boost that will cause your Ground Slam to do additional damage, which could make the difference in a critical situation.
For the bruiser build, things are different. Instead of maxing out one skill over another, the idea is to build Ground Slam and Brutal Strikes alternately when Unstoppable Force and Seismic Shard aren't available for upgrade. This allows a good damage dealing combo while still providing scaling attack damage with Brutal Strikes active.
Unstoppable Force is pretty self explanatory, get it whenever possible. If you didn't know to do this already... c'mon.

It doesn't really matter which one of the two ways you choose to build, you're gonna be tanky enough to survive most of the game without problems. In spirit of this, your role is what I like to call "Useful Troll". See, what you're doing is helping your teammates as much as possible, but doing so in a way that maximizes damage output. Lets see a scenario:

Alright, your AD carry is Caitlyn. She's mid, doing her thing, owning Annie like a boss. All of the sudden, the enemy Cho'Gath and Udyr are upon Caitlyn, who ran out of mana harassing Annie. They begin chasing her, and are getting her down pretty fast. Annie follows, but keeps a distance, just hoping for an assist, because she has next to no health left. You're close enough to ult anyone you want, so what do you do? Go for the kill on Annie, or pop up the Cho'Gath and the Udyr? Trick question, you get both. Assuming the Cait has any common sense, she'll attack the Udyr and Cho'Gath as they are rendered useless by your ult, and subsequent combo. This will probably lead the Annie to come help Udyr and Cho'Gath, setting her up to die by your hand. Meanwhile, Cait is either safely away, or attacking Udyr and Cho'Gath as they switch to focusing you. You pop a Seismic Shard on the high-MS enemy (Udyr in this scenario) and run back to defend your Cait until she's safe enough to fight again, yelling "Trolololol" the whole way since this all took about 4 seconds to go down.

Of course, this is a scenario, not everything will go down like this, but it's a scenario that I've seen more often than not against a carry or squishy in game. In the event this or something like this does happen, you have to account for play-change. Don't assume that you can pop your ult on Cho'Gath and Udyr and chase Annie down- you'll scare the **** out of her. Let her think she has a chance at a kill or assist, and play that against your enemies.

Oh, and when your team gets ganked by the entire enemy team, you NEED to protect your more valuable teammates (carries, hardcore supports, etc.). If they're getting chased down, and an enemy with 2 health is running in the opposite direction, save your teammate- you can still ping the low-health enemy, and hope someone else gets them- just don't waste your ult trying to get a kill and sacrifice your team.

Farming is pretty straightforward on Malphite. You should try to get a laning partner with limited minion farm needs, or offer to solo if your team has a jungler. If you can manage this, then just attack normally and alter appropriately for last hits. Once your Brutal Strikes is up, try to stay at the minion line as much as possible, to get them down as fast as possible, and possibly farm multiple minions at once.

The other key thing to do here is to focus the caster line. They don't do much damage to you, they are easy to get down with Brutal Strikes by altering your main target, and your minions will then focus the melee minions. By doing this, all of the minions should be low at the same time. This is when you can then Ground Slam for a sextuple farm, making you over 100 gold instantly if you're successful.