Metalgun Slinger is a Japan-only 2D platform game for GBA set in an old-western Sci-fi world. The player controls a blue-haired boy who finds a special gun. The game is similar to Mega Man or Contra - run right, jump on platforms, avoid obstacles like holes and spikes, and shoot enemies. The player can slide into enemies, run and shoot simultaneously, but cannot shoot at an angle and run simultaneously. Sometimes the player ride on a bike (the hero's friend drives while the hero kills enemies) or must fight against bosses such as a green-skinned mutant with a mohawk. The hero's weapon, a special revolver, can be upgraded.