The Metal Gear REX is a Metal Gear model designed by Hal "Otacon" Emmerich
as a secret project for the U.S. Department of Defense. Like other Metal Gear units, REX is a bipedal walking tank with the ability to launch nuclear weapons. When Liquid Snake
leads the members of FOXHOUND
in the revolt on Shadow Moses Island
, he threatens to use REX to launch a nuclear warhead unless his demands are met.
Towards the end of Metal Gear Solid
, Solid Snake
confronts the REX as Liquid pilots it. On advice from Otacon, he uses rockets to take out the large radar dish mounted on its right side, disabling the visual systems inside REX and forcing Liquid to fight with the cockpit open. Snake is then able to take out down both Liquid and the REX.
Many years later, in Metal Gear Solid 4: Guns of the Patriots
, Snake returns to Shadow Moses Island during the game's fourth act. In need of an escape, Snake is able to pilot the long-dormant REX after Otacon is able to make it operational again. He makes his way outside, where Liquid Ocelot
confronts him in a Metal Gear RAY
Even though the RAY was designed as an anti-REX Metal Gear, Snake manages to come out on top, and escapes Shadow Moses Island a second time.