[3] The Metal Gear weapon has been consistently described as an all-terrain, nuclear-equipped, walking battle tank capable of launching a nuclear warhead from anywhere on the planet.

Metal Gear is stored in a room guarded by two laser cams and never actually becomes operational; the final challenge is instead a battle with Outer Heaven's mystery leader and a race against time to escape the self-destructing base.

In the non-canonical sequel Snake's Revenge (that was released in the west for the NES), mass-produced versions of the original (dubbed "Metal Gear 1" in the game) are stored inside an enemy cargo ship.

Metal Gear REX has near-impenetrable compound armor, a pair of 30 mm gatling guns,[6] anti-tank missiles, and a free-electron laser, to protect itself from conventional forces.

It also possessed a radome, a satellite antenna-shaped object on REX's left side that provides information about the environment outside of the cockpit while keeping the pilot safe from harm, and increasing the accuracy of all weapons as well.

The pilot is also forced to expose himself to enemy fire, by opening the cockpit in order to see outside (a weakness deliberately built into REX as a "character flaw").

The story of Metal Gear Solid shows weapons company ArmsTech president Kenneth Baker bribes DARPA chief Donald Anderson to get covert U.S. Government funding for Metal Gear REX's development for the U.S. Army, and sends the single prototype to be tested at a nuclear weapons disposal facility on Shadow Moses Island.

While RAY has a pair of Gatling guns and missile launchers on its back and knees to defend itself from more conventional battlefield threats, its primary weapon is a powerful water jet cutter, which can cut through heavily armored foes, such as Metal Gear derivatives.

Its interior workings are also somewhat organic, as it has artificial fibers that contract when electricity is applied, much like natural muscle, instead of typical hydraulics; this pseudo-muscle tissue makes it very maneuverable.

Arsenal hidden under the Big Shell has an unspecified number of "Tengu Commandos", soldiers clad in powered armor and armed with P90 submachine guns and high-frequency blades.

But as Emma's virus slowly destroys GW, Raiden is able to enter Arsenal Gear and uncover the many layers of deception concealing the true meaning behind everything.

A scene showing Arsenal crashing through and destroying several buildings in Manhattan Island but was cut from the final version because of the terrorist attacks on September 11th.

This is possibly due to the fact that, though a walker like Metal Gear would ultimately prove to be a far more versatile system, the Shagohod was only an unusual combination of technologies that already existed at the time (tanks, ground effect, IRBMs, and booster rockets), as opposed to an unrealized idea requiring years or even decades of research as well as incredibly large amounts of money to produce.

Unlike the future bipedal models, this Metal Gear's design is quadrupedal and its nuclear function is to act as a mobile launching device for MIRVs.

With their widespread adoption by PMCs and their ability to perform a variety of combat support roles, they have largely supplanted conventional means of armored warfare.

The Gekko is incredibly agile, maneuverable and dexterous, thanks to its organic legs; made from artificial muscle tissue, cloned from embryonic stem cells of ungulate embryos (later models would supplant these cells with Carbon Nanotube Musculature), these legs allow the Gekko to pick up a man and throw him hard enough to penetrate a brick wall, deliver a kick that can overturn a 6x6 truck, dodge an RPG (and kill its operator), scale walls, crouch to enter buildings, run at speeds equivalent to a motor vehicle, and leap huge distances through the air.

This unit is similar (albeit a bit more angular in appearance using an OLED screen and has wheels instead of feet) to the Snatcher version and is controlled by Otacon.

It is designed to be fully self-supporting, with an array of anti-personnel weapons used to defend itself, and a protocol that calls for it to recognise and eliminate all threats to itself before launching its nuclear missile.

Developer Huey and MSF sub-commander Kazuhira Miller named the mech in honor of Granin's "Metal Gear" design philosophy and the Zero fighter, which was codenamed ZEKE by the Allies in World War II.

Although it is AI-controlled in its testing stages, in the game's true ending shows that Paz Ortega Andrade has modified ZEKE to be manned and uses the mecha to attempt a nuclear strike on the US east coast, forcing Naked Snake to defeat her and heavily damage the unit.

However, when the MSF gets word of an IAEA inspection team coming to visit Mother Base, the unit and its warhead is lowered to the sea floor.

The unit appears to be modeled by crabs or arachnids, with its front legs doubling as retractable blades that can alternately be used to crush or cut its way through armor, buildings, or the earth itself.

The unit has a spherical cockpit that is mounted on a gyroscope; however, due to the system's limited physical control, the machine's arsenal, and its full range of movement, only nanomachine-implanted pilots can operate it.

Unlike previous units, Metal Gear EXCELSUS was purely designed for asymmetrical warfare, capable of causing collateral damage without breaking stride.

In 2018, Raiden encounters a Metal Gear EXCELSUS unit at the Shabhazabad Air Base in Pakistan, piloted by Colorado senator and presidential candidate Steven Armstrong.

Designed by Emmerich and mass-produced by the Soviet Army, it is a bipedal infantry support unit that serves as one of the player's modes of transport, having wheels in the legs for added speed.

Lead engineer Emmerich described the choice of depleted uranium as being a direct result of the need to keep the weapon's mass to a minimum despite ceramic armor offering better protection.

Metal Gear GANDER is the result of the U.S. Army's "Project Babel" after the U.S. Government procured the data from the original prototype in Outer Heaven.

One of the larger Metal Gear models, KODOQUE has two armor-like plates on each of its arms that come equipped with a remote control missile launcher.

SaintLogic developed the Metal Gear for that purpose, but Dr. Thomas Koppelthorn stole Chaioth Ha Qadesh as a means to get revenge for his wife Lucinda and kill all involved in the Praulia Massacre.