Once the technical specifications of Metal Gear Rex were sold on the black market after the Shadow Moses incident, Metal Gear variations quickly began to propagate throughout the world. In response to this threat, USMC General Scott Dolph spearheaded the construction of the Metal Gear Ray prototype, an amphibious, anti-terrorist battle tank with a primary purpose to act as Metal Gear deterrence, eliminating any Rex vehicles that might pose a threat to national security.
Metal Gear RAY possesses a wide array of munitions well beyond its predecessor Rex: Along with Vulcan cannons, guided missiles, lasers, and a rail gun, RAY's arsenal also contains a Hydro Cutter that can fire sea water at super-pressurized velocity, capable of penetrating almost any substance on Earth.
RAY was constructed from materials that make it much more agile and organic than previous Metal Gear models. It can also form a blood-like coagulating nanopaste around any hull damage it sustains.
The Manhattan Incident
Before RAY's attack on the Big Shell, Solid Snake and Otacon landed on a tanker ship were they believed that the Marines were making a Metal Gear of their own as a response of the other types of Metal Gears bring built around the world. As Snake and Otacon were getting close to exposing the Marines' black project Revolver Ocelot and a Russian Army led by Sergei Gurlukovich to take Metal Gear RAY for themselves. Sergei wanted Metal Gear RAY, believing that it would help Russia become a true world power again. However, Ocelot betrayed Sergei claiming that the motivation behind the betrayal was to bring Metal Gear RAY back to the Patriots. As a result, Sergei attacked Ocelot, however, Ocelot blew up the tankar ship and escaped with Metal Gear RAY.
Ray appeared again as Solidus Snake was going to kill Solid Snake and Raiden on top of Arsenal Gear. It was yet again piloted by Liquid Snake. Liquid claimed that he found out who were the people behind The Patriots and was going to kill them, most likely using Ray was the weapon of choice. As a result, RAY jumped back into the ocean with Solid Snake running after to him to capture his demented brother.
Liquid Ocelot's Insurrection
RAY was yet again piloted by Liquid for the last time at Shadow Moses where Snake was using Rex in order to stop Liquid from launching a nuclear missile in space. The two most mercilessly and even though Snake was piloting the inferior Metal Gear, he still won non the less. However, Liquid managed to escape to a personalized version of Arsenal Gear and ran away. When Snake and his team mates were able to catch up to Liquid he released several mass produced RAYs to attack their submarine. As they were about to attack, Snake was able kill Liquid and Sunny input a worm cluster that made all weapons non-functional and thus the RAYs stopped working.