In 2102, the United Earth Government is fighting a losing three-year war against the Dark Axis, a military dictatorship commanded by the tyrant Venkar Amon. The Metal Warriors—a freedom-fighting unit fielding robotic combat suits—are among the few groups still actively resisting. Playing as Lieutenant Stone, missions begin in orbit: rescuing agent Marissa from the Axis station Axis 5, capturing enemy supply lines, and seizing an asteroid base for resources. Success earns Stone a field promotion to Captain, but it also draws the Axis's full attention. The campaign moves to Earth—disabling an Alaskan anti-aircraft cannon, fighting through a bombed Chilean city, and ultimately storming the Axis command center where Venkar Amon's secret superweapon is under construction. Stone defeats Amon in a final battle between flying armored suits; Amon is incinerated with his own base, and Stone escapes the explosion with his Nitro suit wrecked.