Mark VI: The Mark VI armor differs little from the Mark III and Mark IV platform; the main difference being a triangular-shaped chestplate protecting the arc reactor assembly. This suit withstands prolonged and extreme combat situations with relatively minor damage, and is shown to be extremely fast and responsive in flight, and strong and durable in hand-to-hand combat. The new model seemingly retains all the weapons present in the Mark III and Mark IV, with two additions: a multi-fire adhesive grenade launcher in the upper arm, and a one-time-use hand-mounted laser weapon, powerful enough to cut though several Hammer drones cleanly in half. The Mark VI armor's look originated from the Extremis armor in the comics.
Arc Reactor: In the first movie, the armor suits are powered by a miniaturized arc reactor, a fictional clean energy source. The arc reactor is also used to power the electromagnet that protects Stark's heart from the shrapnel embedded in his chest. The first reactor was allegedly capable of powering the electromagnet protecting Tony's heart for fifty lifetimes on its own, but after returning home Stark developed a more efficient reactor that he used to power the Mark II and Mark III suits as well. Although Stark reverted to the original reactor after the new model was stolen by Obadiah Stane to power the Iron Monger suit, the reactor had great difficulty providing enough power to the Mark III suit, being depleted to around a fifth of its power supply simply by flying Stark from his home to Stark Industries, with the last 20% being exhausted during his fight with Stane in the Iron Monger armor.
The Mark III armor included anti-tank missiles that launch from the suit's forearms, steering and retrothrust jets in the palms which could double as short-range repulsors (early in the first film, Stark mentions that the Jericho missiles utilize his company's repulsor technology), small anti-personnel guns in the shoulders which could be individually targeted at multiple enemies for a simultaneous attack, flare launchers on the hips, and a uni-beam projector in the center of his chest. Furthermore, Mark II and III operate with remote assistance from JARVIS (Stark's artificial intelligence), who manages the armor's systems at Stark's command, and they also have a holographic HUD. These armors also have variable control surfaces for active flight control, which are controlled by JARVIS to automatically stabilize the suit in flight. All three suits are able to protect their occupant from the effects of extreme g-forces.
The second movie reveals that the miniaturized arc reactor was first developed some years earlier in a joint effort between Howard Stark (Stark's father) and Russian physicist Anton Vanko (the father of Ivan Vanko). Also, the miniaturized arc reactor (palladium) that Stark has been using for a power source in the previous version was slowly poisoning him. When Stark successfully develops a new element (vibranium) for a power source of his personal arc reactor, he must develop a new suit (Mark VI) capable of channeling the immense power.