Doctor Will Magnus was the preeminent robotics scientist on Earth-One, and when motivated to create artificial life based on metallic elements his Metal Men was spawned. While first viewing this team of Gold, Iron, Lead, Mercury, Platinum and Tina as mere expendable pawns... Magnus grew in his affection towards this team. And even after experiencing a period wherein he was brainwashed and temporarily evil, he still proved his loyalty to his team in the end. At times Magnus actually imitated the adaptability of his creations before regaining his humanity.
During they're memorable career the Metal Men met the Atom, Green Lantern, Superman, Batman, Wonder Woman and several other heroes while aiding the caused of justice. And despite becoming fugitives of justice from time to time due to misunderstanding with humanity and during periods when Magnus' more off-center moments, the Metal Men on Earth-One truly endeared themselves to mankind and were seen as useful tools of the American military on different occasions. Such was not the case for their counterparts a universe away.
And the man behind the appearance of Metal Men from (a) Jupiter on Earth-Two, Hubert Crawford, was also a prominent scientist although his predictions of a robotic invasion had been scoffed at for so long he grew bitter. After contacting these robotic creatures, he obtained their unique attributes and incorporated them through some undisclosed process into his body.
Becoming a type of elemental man, somewhat like the second Metamorpho of Earth-One, architech Edifice Bulwark, Crawford's criminal career was short-lived after the combined teamwork of the Justice Society ended up defeating him like they had his inhuman minions previously. Whether or not he ever did setup a laboratory with the JSA's help to create other creatures like the legion of robots in unknown. But if he did, would they have had those nifty antenna?