Read more about Metallo at: Wikipedia
Official Site: DC Comics
Metallo (John Corben) is a comic book supervillain and cyborg who appears in Superman stories published by DC Comics. Metallo's trademark is his kryptonite power source, which he often uses as a weapon against Superman. His traditional identity is John Corben. The character first appeared in Action Comics #252 (May 1959).
In 2009, Metallo was ranked as IGN's 52nd Greatest Comic Book Villain of All Time.
The Golden Age Superman battled an unnamed scientist calling himself "Metalo" (note the alternate spelling) who wore a powered suit of steel armor in a story titled "Man of Steel Versus Man of Metal". Years later, Superman encountered the villain a second time in a story with the same title. Metalo, his real name now revealed as George Grant, had a new suit of armor and had also taken a serum to increase his personal strength to superhuman levels. He exposed Superman to a ray that reduced the hero's 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 easily defeated Metalo.
Metallo appeared as Jor-El's robot to battle Superboy, in Superboy #45 (1956), but this version of Metallo is not to be confused with the better known John Corben version, who would appear later in the Silver Age.