Roger Corben was the brother of John Corben, the first Metallo. He was severely injured by falling debris during a robbery of S.T.A.R. Labs. He allowed the criminal organization SKULL to attach his severed head to a leaden cybernetic body powered by a Synthetic Kryptonite heart in order to seek revenge on Superman for his brother's death. He initially assumed the identity of WGBS Associate Producer Martin Korda, but this ruse was quickly discovered.
Metallo challenged Superman numerous times over the years, as well as the likes of Batman and Blue Devil. Eventually he was absorbed by a black hole he had himself created, and so presumably perished.