Doctor William Magnus, and his fantastic Metal Men, have been taken captive by the robot queens of an alien world. Having eaten of the food provided, Magnus, and the Metal Men, have grown to gigantic size. All save Tin, who consumed nothing. As Tin is the only Metal Man still capable of fitting inside their escape rocket, Tin is sent back to Earth. Though Magnus, and the Metal Men, have momentarily escaped the robot queens, their flight is hindered by the charm bracelet linking them all together. On the horizon, Platinum spies the robot queens, led by a pack of robot dogs. Frantically, Magnus, and the Metal Men, bury themselves in the sand, to elude their pursuers. Magnus notes that the robot dogs, really subservient male robots, could have found them, but seemed to lead the robot queens away.
As they pass, one of the robot queens decides to mark the trail. Her energy beam fuses a large area of sand into glass. Magnus, and the Metal Men, are completely encased. To make matters worse, an enormous mechanical raptor plucks them up, carrying their entire glass prison into the sky. The mechanical raptor is attacked, mid-flight, by another robot bird. While the two machine raptors fight over them, Magnus, and the Metal Men, are dropped into a massive bird's nest. One of the "eggs' hatches, releasing a smaller mechanical raptor. Iron manages to find the flaw in the glass prison and shatter it. Platinum draws her torso out into thin wire, and binds the raptor's beak closed. Her sacrifice allows the others to escape the nest. With Platinum still linked to the bracelet, Iron and Gold are able to reel her upper body back down to it's extremities.
Unfortunately, this action also carries the raptor down with her. Lead molds himself into a sledgehammer, which Iron uses to shatter the raptor. Unwilling to abandon his comrades, Tin turns the rocket around, re-entering the planet's atmosphere. The robot queens immediately begin firing at the rocket. Pulling at their leashes, the robot "dogs" are able to spoil the queens' aim. Though Tin's rocket is damaged, it is not destroyed. Tin finds himself on a collision course with Magnus, and the Metal Men. Tin manages to put the rocket down in a nearby lake. When he doesn't surface, Magnus, and the Metal Men, go in after Tin. In their haste to rescue Tin, the Metal Men are unaware that they have placed Magnus' life in jeopardy, as, unlike the Metal Men, Magnus cannot breathe underwater. An enormous mechanical crab closes on the rocket.
Platinum realizes the Magnus is drowning. Hastily Gold molds himself into a submarine around the team. Iron and Lead mold themselves into torpedoes, which Gold then launches at the machine crab. With the mechanical crab destroyed, Iron and Lead return to the "submarine". One of the robot queens fishes Tin's rocket out of the lake. Gold follows, only to be snatched up, as well. Still hindered by the bracelet, the Metal Men fight back agains their captor. With the team under a barrage of laser fire, Platinum is just able to reach the key to the bracelet, imbedded in the robot queen's chest. Quickly, Platinum turns the key, freeing the team. An impassioned speech from Platinum stirs the "dogs" to their feet. Throwing off their leashes, the formerly subservient male robots rise up against the tyrannical robot queens. At the end of their revolt, the robot males are triumphant. The robot queens are dead. Magnus, and the Metal Men, return to their rocket, and set course for Earth.