Unstoppable Force is one of the best initiating abilities in the game, as it transports Malphite to the target location and knocks up all nearby enemies. Malphite is also immune to disables during the dash.
Remember to allow Granite Shield to recharge if a team fight is about to start.
Seismic Shard is a strong ability with several utilities:
It can be used for harassment and poking in lane, with some mana regen.
Malphite's standard combo is first activating Brutal Strikes, slowing an enemy with Seismic Shard, charging in with Unstoppable Force, then ending with Ground Slam. With a high amount of armor, this combo can shut down multiple enemies at once, especially if they're melee-DPS.
Malphite excels at being an anti-carry, designed to stop carries in their tracks with his Ground Slam and then destroy them with his high damage output.
Malphite can make a strong counter to certain solo top champions, such as Tryndamere, Irelia, or Jax that have few ranged options and need to auto-attack to secure lane control. Use Seismic Shard to harass and Ground Slam to interfere with last hits, giving you free reign to farm yourself.
If your enemy is on low health and they are behind a wall, Unstoppable Force can go through walls and you can pick up a kill easily.
Conversely, if you are low on health and are at great risk of dying, Malphite'sUnstoppable Force can be used to escape.
Jungling works especially well on Malphite as his Ground Slam can negate most of the Ancient Golem's damage at level one along with Granite Shield, meaning that Malphite can kill the Ancient Golem on an offensive or defensive combination of starting items and potions. After acquiring Seismic Shard and the buff from the Lizard Elder, Malphite can gank lanes to moderate effect, but can do so to the greatest effect against weak, autoattack-dependent AD champions like Ashe or top lane Sion.
It should be noted, however, that his passive, Granite Shield, scales with maximum health, so planning on building a health item first, even if you are unsure what your endgame build will be, is a wise choice. This will also grant you some early game tankiness and survivability to help you through laning phase.
Malphite is typically built for a tank role but can be built with ability power, trading off late game utility for damage.
Ground Slam will often be your primary damage ability, so buying items like Frozen Heart that give you armor and cooldown reduction or Thornmail will help tremendously. Building DPS/Tank gear and he becomes a deadly initiator and anti-carry.
Note that the health regeneration is pathetically small during the actual teamfight. It will get you at most +120 health for a fifteen second teamfight. Health Regeneration is much better during the laning phase, and drops off significantly in usefulness during teamfight situations.
In the lane, try to harass Malphite to break his Granite Shield and prevent its regeneration.
When chasing or being chased, it may be a good idea to hold on to any movement speed increasing buffs you may have until after he has used Seismic Shard as your speed increase will also increase the amount of movement speed he steals.
Wait until the effect of his Brutal Strikes wears off before continuing to attack Malphite as it gives him armor.
If you are using a champion whose primary damage source is from auto-attacks, try to stay out of range of Ground Slam, as this will reduce your damage significantly.
Since Malphite is more likely to build armor than health, he will be very susceptible to high burst from magic damage. Consider this when picking champions to counter him.
Avoid grouping together with your allies to decrease the impact of an Unstoppable Force.
Malphite can be effectively countered by going double AP, as opposed to the usual bruiser meta.