Hello people, this will be my first time writing a Guide (not in-depth) But if you notice something wrong, please tell me so that i can correct it.

My Rune choice is 9 Marks of Magic Penetration so you can harass the enemies in lane together with Doran's ring to give you a little boost on the attacks and still give you mana regen.
The other runes i chose, are for Armor and Magic Resistance because in early game you don't want to die that fast, if enemy has armor penetration, well kill him before he can kill you :D
Quintessences i chose Movement Speed because, being a tank you don't wanna arrive to the battle field late now do you ? having 4.5% Movement speed in runes + 4.5% in Masteries allows you to run decently fast so you don't lose your lane and you can help other lanes.

Tank masteries i use those because i wanna get as much armor and protection as i can, Mercenary just to get some boost gold, if you want you can remove 1 level to mercenary and give to Movement Speed. 4.5% + 3% (Initiator) + 2% (Swiftness) might not be a bad idea, seeing as you get 9.5% more movement speed, so its good :D

For first item, you might wanna get a Doran's ring so you can deal some decent damage early in game. Your lane partner is probably good enough to cover the lack of Doran's Shield.
After Getting Mercury threads, slows wont affect you as much and you can now chase down enemies fast thanks to your Movement speed :D

Sunfire cape for farming and killing running away enemies just by standing by them. when you have no mana and the enemy is running away with like... 20 HP or such ? just chasing him down will kill him. Sunfire Cape + Brutal Strikes + Ground Slam = Good farming.

Frozen Heart, because malphite's mana is low and it gives armor and cooldown reduction, excellent :D

Force of Nature, More Movement speed, more magic resist so why not ?

Warmog's Armor, Look, its health!! Why not?? health, kill minions? more health, kill champions? more health. you can stand longer against enemies too.

Guardian Angel, To piss of people who dont like you, if they have to many AD characters, take Thornmail instead ^^

Since i support the Cookie (Seismic Shard) Spam, i recommend you take Clarity and flash to run/chase opponents. You can take Ignite instead, but that will make you dependable on the Ring's mana regen.

Attempt to master Seismic Shard (Cookie) as fast as you can, followed by Ground slam. at first, get Seismic Shard to harass as i said before. Next, raise Ground Slam and then Brutal Strikes, leave Brutal Strikes at Lv.1 till you max all the others because (for me) the more damage i take by harassing, the faster my lane partner kills. Ultimate, Unstoppable Force, must be leveled whenever you can.