Mithral Gun: Biomechanical is a single-player game of action survival. It tells the story of a dispute between robots and humans at the end of the 24th century, in which players as BIOs of mechanical girls survived in the battlefield.

Game play is based on survival and combat. Unlike traditional survival games, players control robots without food and water, they need power and energy; the damage of robots can not be recovered naturally, they need to find materials to repair, but also can make more detailed modifications.

The background of the game is in the period of war between man and robot. As the protagonist of robots and human and robotic forces are in a hostile state, players need to survive in a war zone full of hostile forces, or become friends with one force, relying on other forces to survive.

Players can find all kinds of weapons and equipment available in the ruins. Weapons themselves have durability settings, each repair will gradually reduce the durability limit, which requires a reasonable arrangement of the use of weapons and material consumption, through a variety of tactical ways to solve the enemy.

The game contains certain random elements. Every time a player starts a new game, the map changes: for example, the location of the NPC and the safe house changes randomly, and enemies in some areas also differ.