Metallo () is a supervillain appearing in American comic books published by DC Comics, commonly as an adversary of Superman. Metallo is usually depicted as a cyborg with a kryptonite power source in his heart, which he uses as a weapon against Superman. In 2009, Metallo was ranked as IGN's 52nd-greatest comic book villain of all time. Publication history John Corben and Metallo first appeared in the Superman comic strip storyline "The Menace of Metallo", which ran from 15 December 1958 to 4 April 1959. The character debuted in comic books in Action Comics #252 (May 1959), in a story by Robert Bernstein and Al Plastino. There was an earlier "Metalo" who appeared in World's Finest #6 (Summer 1942). This was just a man who discovered the most powerful metal on Earth and invented a strength serum. Fictional character biography George Grant Metalo (note the alternate spelling) is the identity of an inventor/scientist named George Grant who had built a powered suit of armor made from "the most powerful metal on Earth" as well as a "strength serum" that made him a near-match for Superman. To draw him out, Metalo captured Lois Lane. At the end of their battle, Metalo fell into a crevice to what Superman assumed would be his death. Metalo was revealed to the reader to have "narrowly escaped destruction" and vowed to take revenge. Nearly 40 years would pass before the character reappeared in print to challenge Superman again. Metalo had improved his armor and serum and also exposed Superman to a ray that reduced his power significantly, giving Metalo superior strength in their first battle. Superman engaged in a lengthy regimen of exercise and training to restore his powers and returned to easily defeat Metalo. Jor-El's Robot A different Metallo appeared as Jor-El's robot to battle Superboy. John Corben John Corben was originally a journalist (and secretly a thief and murderer) who had just committed what he thought was the perfect murder. While fleeing from the scene of the crime, he suffered a near-fatal accident that mangled his body beyond repair. An elderly scientist, Professor Vale, happened to come upon him and used his scientific skill to transfer Corben's brain into a robotic body covered by a flesh-like artificial skin. Corben discovered that his power source, a capsule of uranium, would only last one day, but was told by Vale that kryptonite would provide him