Please note that I only put four items in each build because you will come across different enemy team builds and I am trying to get you to see how to choose best again them.
These are the basic ideas behind builds I use for Dominion. If you have have any questions/comments/ideas please post them. Malphite is the best tank imo for dominion. He can defend a turret against an entire team(I've done it with a little bit of luck) and can Turret dive any enemy champ who is around 50% or fewer Hit Points.

Also my ingame name is tcweeze if anyone needs a decent tank on their team. Dominion or otherwise.

The reason go 6 x flat armor and magic resist/ 3(per level) is simple. Early game everyone is going for as much AD/AP as they can squeeze out of the starting gold. These give you great Armor and Magic Resistance base stats to start with and help you get the boots that you need as the first item in your game. Let me repeat, your FIRST item should be completed boots before you leave the base.

I choose to go 9 x Magic Penetration to give myself an early edge against whoever I am facing on the bottom lane. You are a tank that can poke any champion at your own will on the bottom lane. This helps immensely.

Quintessences are a bit more difficult to recommend when playing a match in dominion. I chose Avarice to help me return to base if I need to, Fortitude because every little bit counts(although if you feel you could use MR or AR here feel free), and finally Resilience(I lean more towards Armor than Magic resist early game).

This rune setup should give you a well balanced defense for any adversary early game. Even if you get knocked around a bit you can always retreat to base and be back on the closest bottom turret fairly quickly.

Nothing much to explain here except the less time you spend dead the better. Especially in back and forth games. These choices help you get Armor and Magic resist quicker early game. If you have any other recommendations please feel free to post as I will update the guide with different options that I can't think of right this moment.

His passive is self explanatory

My justification for leveling brutal strikes last is because most games I get one point into the skill before the game is over. It isn't as necessary as your Q and E skills. This is my personal preference and it only works in dominion right now.

Seismic shard- This gives you great early game poke(Yes a tank who has a decent poke) and coupled with your runes of Magic Penetration annoys any champion you come across. Tank or otherwise. It also helps you burst down enemies later coupled with Ground Slam.

Ground Slam- The second most important in your skill sequence also does decent damage at any level. If you find yourself alone with one enemy champion this skill helps you force them to retreat or even better use their flash.

Unstoppable Force- Turret dive/Turret interrupt. Great range skill that when you get your Frozen Armor has decent recharge time and has several different uses.

Garrison- A must for Malphite! Allows you to use Unstoppable Force against an enemy who is hugging their tower. Save this Spell unless you feel like you team can cover the bottom turret without your assistance. Great defensive ability and is a must for Malphite even if you are heading for the Windmill early game.

Flash- I see a lot of people going Ghost for Dominion. You have enough speed increase buffs on the map that you do not need Ghost and Flash is simply the better Spell.

If you are getting 2v1 and are taking a good amount of damage hit one of the enemies with your Seismic Shard and(make sure you do not have any slows stuns etc. on your) flash away. You can also(if feeling bold) chase an enemy who has little to no hitpoints and queue up your Seismic Shard and flash towards them if the flash will put you in range. Only works if you have line of sight at the end of the flash but a great way to finish off an enemy.

The runes/spells/masteries I have outlined above allow for a lot of flexibility. The game will be decided on how well you can judge the enemy team. I will try to give you the basics on what I look for on an enemy team.

I subscribe to a 2 to 1 creed when playing dominion meaning that for every 2 Magic Resist/Armor Items I complete I build one in the opposite direction(2 MR 1 AD, 2AD 1 MR). The exception is when you have an AP/AD heavy team meaning 3 or more of each or a 2 AD/AP team with 2 hybrids. In that case pay attention to what items the enemy builds first and change to suit them accordingly.

For AD Heavy Teams(2 or more AD Champs)
This build includes:

2 AD, 1 hybrid, 2 anything
3 AD, 2 Anything
3 AD, 1 hybrid, 1 anything

On both malphite builds that I listed the runes, spells, and skill sequence are the same.
The important part of this build is getting Armor boots and getting your second item within the first 30 seconds of the game. If you are going up against any of the teams listed see who goes bottom first. If you get an AP Champ wait around your turret until you have 700 gold saved and hit the b button. By the time you return you will be able to afford a Negatron Cloak and can be back at your turret before they can get to it. Grab a health pot or two just in case.

Once you have both an MR item and an AR boots you can begin poking the champion on bottom. Use only your Seismic Shard until the champ is either pushed back or has to return for health. While you are poking the champion it is important to kill as many minions as you can while tanking the little damage that the enemy can output. In many instances I charge them once they are at 50% and get a couple of hits in before they either flash or retreat. Keep pushing creeps if they just hang out at their turret but if they return go straight for their turret and begin to take it. If you are lucky you can get their turret down below half and you have a decent creep wave following your lead. Once the enemy champ(or one of his buddies comes to defend go straight for their health pot located near their turret. Even if you do not have any hitpoints missing you are taking away their ability to heal when they get in a fight with you.

At this point you should have a enemy champ who has either lost their turret because of your creep wave and is at 50% or lower hitpoints or you have flat out taken the turret and are in defense mode with decent amount of hitpoints. In either case now your judgement comes into play. Does your team have 3 turrets or 2 turrets? How many of your allies/enemies are dead? From here you can begin to build your Frozen Heart. When I return to buy more items I always look to see what the other team is building. If I see more AD items I get more Armor, If I see more AP Items I get more MR. You have to be on your toes when Playing Malphite and rely heavily on your team to keep the windmill in your favor most/if not all of the game. A good Malphite never has to leave the bottom turrets and even gets 2 v 1 several times. The more you can draw from the other turrets and focus on you the better. You are a tank. ;)

Optional:
If you team is doing good you can use your Garrison spell to charge an enemy turrret with one or two enemies in it. Do this only if you feel you can attack them and either force them out or kill them.

AP Heavy Teams

2 AP, 1 hybrid, 2 anything
3 AP, 2 Anything
3 AP, 1 hybrid, 1 anything


Take everything I said in the previous paragraphs and switch out the AP/AD to the opposite. I suggest Mercury Treads buying outright in case the enemy team has 3AP Champs and one hybrid(also if you think they champ will have high magic penetration). The boots will be enough to keep you in the fight early.

DO NOT go top unless you have a well balanced team with another tank(preferably Alistar or Garen).
DO NOT get any items that increase your AP/AD unless you also get a fair amount of armor/magic resist with said item. The only one worthwhile is Abyssal Scepter.
DO NOT go for a high k/d ratio. You are a tank. If you want kills go play something else.
DO NOT CHASE enemy champs unless you can kill them and take their turret shortly their after.

The reason that I only put a few items up top is because this build is very flexible when it comes to player style:
MORE HP
MORE REGEN
MORE WHATEVER

Try to save flash and Garrison until necessary to use. I tend to let my turret get down to 25% hit points before I consider using Garrison.

Occasionally you can let someone else cover bottom after the game has started and go around harassing the single enemy champs who are trying to backdoor your turrets. In that case take as many shots and you can give/receive and then retreat to a turret or head towards an ally.

Hopefully I didn't confuse you with how I play Malphite. Please post any questions/comments/good/bad that you would like about the build. Also please let me know if I should explain anything further. I assume that most players know a little bit about tanking and what you need to do to keep your team in the game.