For the Silver, Bronze and Modern Age version see: Metallo
George Grant robbed a mail train in his first successful criminal outing. He decided to challenge Superman as his next exploit. He used his scientific expertise to create a powerful metal suit of armor that did not stand up against the strength of Superman.
Years later he would challenge Superman once again. The improved suit of armor, the help of artificially acquired super strength, and a ray weapon which could weaken Superman could help Metalo defeat the Man of Steel. The ray depleted Superman's strength and through a regiment of intensive training Superman restored his strength to his former levels and defeated Grant for the last time.