Term applied to bipedal tanks, designed primarily to launch ICBMs from any point on Earth, thus rendering the concept of nuclear deterance moot, as well as eliminating the need for expensive silos or nuclear subs.
Metal Gears also serve the role of assault, artillery, anti-vehicle, anti-personell, escort, theatre-missile-defence, as well as numerous other functions with their heavy armaments. The numerous models over the decades have been armed with heavy machine-guns, rockets, hellfire missles, laser systems, rail-guns, hydro-cannons, and various other conventional and unconventional weapons.
In addition to carrying ICBMs, Metal Gears have been known to carry cluster-bombs, cruise missiles, and various other assault payloads in its missile tubes.
The Metal Gear is a fictional weapon-system.
No government has stepped forward for the nuclear attack, and no nation can be accused. NATO suspects that a Metal Gear was involved.