Some of the Man of Tomorrow's foes were near identical on both Earths One and Two, such as Luthor, Prankster, Toyman. Others were very different, which we'll be considering throughout the week. And some were... well very similar yet with distinct differences. Metal(l)o was among the latter. And among the most memorable as they were true "Men of Steel".
Roger Corbin was the vengeful brother of John Corbin, a reporter/criminal who's mind was inserted in a cybernetic body. When his brother replaced his uranium power source with what he thought was kryptonite, yet turned out to be a forgery costing him his life, he left behind a distraught brother. Roger himself was setup by the criminal gang known as S.K.U.L.L. into becoming the newest candidate for the Metallo title, and body. George Grant was a criminal scientist inventing an armor built with the strongest known metal discovered, and a strength enhancing serum. After an initial defeat Grant returned years later, utilizing a ray which reduced Superman's powers briefly, yet this was only a temporary setback for Kal-L. Roger himself returned repeatedly to duel with Kal-El and later his pal Batman, each time handed a sound defeat.
It should be noted that on Earth-Two, around the time of Metalo's first appearance, another criminal had his mind transplanted like John Corbin into a robotic body, until he lost his life in battle with that world's Robotman.