Doctor William Magnus, and his fantastic Metal Men, pose for "Picture World" magazine. The heat of the midday sun causes Mercury to elongate, stretching high into the sky. Hurriedly, Lead molds himself into a barrier, to protect Mercury from the heat of the sun. Platinum's amorous advances towards Magnus, prompts the famed inventor to consider donating her to a science museum. Platinum reminds Magnus of how that turned out the first time. When the museum staff had arrived to collect Platinum, she attacked them. Magnus had to order her to stand down, and accompany the staff quietly. In the museum, Platinum had desperately reached out to Magnus, pleading with her creator not to leave her.
Sensing the Metal Men's depression over Platinum's absence, Magnus had suggested taking the Jetaway out for a ride. Soaring over the city, Magnus spied meteorites plummeting into a giant gas storage tank. The meteorites' impact caused a massive explosion. Magnus, and the Metal Men, were pitched out of the Jetaway. Holding onto Mercury, Magnus was carried back up into the Jetaway. Tin attempted to seal the burning gas tank. The gas, though, burned hotter than Tin's melting point, reducing the humble Metal Man to slag. Lead also tried to seal the blazing container, and met the same fate. Iron and Gold were able to seal the tank, but both suffered horrendous damage.
Magnus collected the remains of the Metal Men, and returned to his laboratory, to effect repairs. While waiting for the Metal Men to revive, Mercury molded himself into pretzel shapes, to try to amuse Magnus. The museum curator angrily contacted Magnus, and demanded that he reclaim Platinum. Her constant crying had led museum-goers to believe that she was not actually a robot, but a human girl being held against her will. Magnus had complied with the curator's demands. On the way back, Magnus had Platinum retrieve a sample of the meteorites that had detonated the gas tank. Upon analysis, Magnus discovered that the meteorites were, in fact, machine-made.
Day prior, in deep space, an alien patrol craft had arrived at a junkyard planetoid, to check up on an uncontrollable robot, designated "Z-1". The patrol craft came under attack by, what at first seemed like meteorites, but turned out to be robot duplicates of Z-1. Robots Z-1 collectively called "Missile Men". Z-1's creators had marooned the rampaging robot on the junkyard planetoid, to prevent it from destroying their world. Attempting to build itself a queen, to rule the planetoid by it's side, Z-1 found that it could only build robot duplicates of itself. Using the resources of the planetoid, Z-1 assembled it's army of Missile Men.
Using an incredibly powerful long range telescope, Z-1 spied Platinum on Earth, and determined to make her it's bride. Then, Z-1, and the Missile Men, hurled themselves into the void, destroying the alien patrol craft, on their way to Earth. In orbit above Earth, Z-1 launched the first volley of Missile Men, to test Earth's defenses. It was these Missile Men that detonated the gas tank. After waiting a suitable period for some kind of response from Earth, Z-1 ordered the Missile Men to rain down upon the globe. As the Missile Men plummet into the city, Magnus, and the Metal Men swing into action. The vast numbers of the Missile Men prove too much for Magnus, and his creations.
Injured, and with the other Metal Men downed, Magnus orders Platinum to flee. Z-1 breaks formation to pursue Platinum. Magnus, realizing that Z-1 must be controlling the other Missile Men, targets Z-1 with a magnetic cannon. The other Missile Men are drawn to Z-1, forming an enormous shell of Missile Men around Z-1. The massive sphere of Missile Men fall into the sea, carrying the threat of Z-1 to the bottom of the ocean. Z-1's prison of Missile Men is routinely checked on by the United States Navy. Back at his laboratory complex, Magnus, with Platinum at his side, once more rebuilds the Metal Men.