Con man John Corben was left near-dead in a car accident, until Professor Vale saved him by putting his brain into a powerful robot body. Powered by kryptonite, Corben used his new body for criminal activities, and became a regular foe of Superman.
Due to his robotic nature, Metallo has received lots of upgrades and different bodies over the years. This particular look is based on a design by Ed McGuinness, later used by Mattel for their recent Metallo figure.
The RecipeMetallo is made from lots of Minimate parts. His base is an ordinary Minimate, with feet from a Cylon Warrior that have added toe and knee details from Magic Sculpt. His hands are made from modified Palz hands, glued to the gauntlets from a modern Cylon. His waist piece also comes from a modern Cylon and gives him extra height.
Metallo wears a modified "big chest", which means it has a lot of holes cut into it. Attached to that chestpiece is a piece of kryptonite (made with Sculpty), and a chest plate made with Magic Sculpt. His huge shoulder pads are also made from Magic Sculpt. And the cables at the top of the chest piece are from cut-up Brainiac tentacles.
On his back, I used coffee straws and tiny plastic knobs for his smokestacks and details. Finally, Metallo's face and leg details are from water-transfer decals.