This is my guide for how to build a succesfull malphite which can tank and deal alot of damage.
The build is most succesfull when playing solo lane as getting lvl 6 fastest helps alot.
Hope you find this build usefull and im hoping you could give me some comment as this is my first build written.
I will be updating afterwards, this is v0.7.1 of this build :P

Fixed skill sequence and mastery tree.

As for runes, i prefer to have flat HP, armor and magic res at start so i can be on the lane for longer. I choose to have more armor from runes because malphite's armor at start is not too great. For having more armor at start it gives you boost on dmg reduced + ground slam.

For alternatives you might want to go for all magic res runes except quints to maximize both, armor and magic res of this build thought its only effective against AP opponents.
2nd alt is to switch armor marks to magic pen runes to give more effectiveness to seismic shard at early game, but i dont see this necessary because you will get fed anyways in mid game when shard deals 270+AP

For masteries i picked 21/6/3. Offense is what malphite need's, it would be a waste to make defensive mastery build for malph. As for offensive mastery build it gives you a nice boost in DMG and magic pen + for the res 9 points give you 6 on both armor and magic res and hp/mana regen which is a must when playing malphite as your mana is always drained when using more than 1 ability :D

For items i choose to have tank items as first and then build my nuke part for endgame.
When you spawn buy faerie charm and 1/2 hp pots. When you have over 600cash and have to recall, buy philosopher stone as it gives you hp regen and mana regen.
After philosopher stone buy mercury treads for reducing stuns etc. plus 25 magic res.
Then when you have the money go for sunfire cape for dealing constant dmg and survivability (i think you know the feeling when enemy has like 20hp and gets away because your out of range. having sunfire cape you deny this problem :D)
as for fourth item you need frozen mallet as your last hp item and giving you a change to slow your enemies (obviously its not so low % as it says, when i play, its almost always 100% to slow...)
Frozen mallet ends your tank build as then you will be concentrating on dealing damage with abilities.
Buying rabaddons deathcap and zhonyas hourglass in order does give you great damage when ganking with ultimate.
Now it is up to you if you want to sell philosophers stone and go for archangel staff.
In my opinion its great item for last, as you dont need hp regen at this point (late game) and archangel staff giving you AP and 25mana/per 5sec.

If you want to go for ultimate nuke at long games (over 50 mins) you can sell frozen mallet and buy lich bane to boost AP even more (500-700, dont remember the exact number)
There is few champions who can survive this massive AP/magic pen combo.

For alternatives, you can choose to have force of nature and/or guardian angel instead of sunfire and/or frozen mallet, but choosing this does not give you enough HP (IMO) to play effectively.

For skill's, ALWAYS choose shard as first ability, its your main priority ability, as it deals the most damage and is the only "range" type abi on malphite (ulti not counting).
Priority order goes like this -> unstoppable force -> seismic shard -> ground slam -> brutal strikes.
Skill sequence shown at top, im not sure how the last one's go, but i hope you got the idea from my priority part ^ :P

Okay, its time to play.
Always go solo lane if you get a change! Malphite gets much more potential on ganking when leveling up quicker.

Early game
At this point of the game you should play agressively, using shard to enemy champios always when you can to force them to recall or even get a kill. Use ground slam to farm minions but keep in mind that you dont have alot of mana at start. After getting philosopher stone you can start spamming abilies more.

Mid game
At this point you should have atleast boots of speed/merc treads. After getting ulti you can start observing other lanes if you could do an effective gank. When you see that your opportunity has came you might want to know the order to use your abilies. I do prefer this order -> unstoppable force -> brutal strikes -> ground slam -> seismic shard.
This order gives you the maximun damage you can deal, as unstoppable force gives your teammates few seconds to run in the fight, brutal strikes give you armor + AD which boosts your damage dealt with ground slam and then possibly finishing him off with seismic shard.
You should start tanking dragon as many times as you can and if you need more mana regen go for the golem buff.

Late game
At this point you should already have your full tank items + AP items to boost your damage dealt. You can now start diving to towers, Tanking them raw with your team helping and ganking ultra effectively your enemies. There are few champions that can beat malph 1v1 at this point of the game as you deny 15% of enemys magic res and have over 300 AP at the time.

LAAATE GAME
You are already lvl 18 and have full build and youre thinking what next?
If you still want to go for more damage, you can exchange frozen mallet and/or sunfire cape to lich bane and/or void staff giving you 40+15 magic pen + 700+AP. This is the final build for long games where you just need to kill everyone with an ease of a button press.

I hope this build works with you who ever is trying it.
Please rate it and give constructive feedback as this really is my first build ever made. :)