Very few official Metal Gear PC releases used traditional alphanumeric license keys. The most notable example is Metal Gear Solid 2: Substance (2003). Physical copies required a CD key (often found inside the manual or jewel case) to install. These keys are unique to each copy and cannot be generated by generic online "keygens" (key generators). For modern digital releases (via GOG or Steam), no manual key entry is needed—the platform handles activation automatically.
If you're searching for a "license key" for a Metal Gear game, you’ve likely encountered one of two very different situations: a legitimate product requirement or a common online trap.