40 years ago - John Corben is born.
20 years ago - 20-year-old John Corben, small time thief, starts running cons.
13 years ago - 27-year-old John Corben is nearly killed in a massive car accident. His body is recovered by S.H.A.D.E., who put his brain into a indestructible robotic body covered with cloned body tissue. He escapes and rampages, but it stopped by Superman.
12 years ago - 28-year-old John Corben, his uranium core nearly depleated, steals a krytonite stone from Lexcorp as his new powercore.
6 years ago - 34-year-old John Corben is recovered by General Wade Elling for his ultramarine project, his hardware updated,. He escapes and rampages, stopped by Superman.
1 year ago - 39-year-old John Corben has his core programming is rewritten by Brainiac's data modules, becomes able to rebuild his body. He ncapacitates Superman, but is defeated by M'gann M'orzz, Natasha Irons and Traci Thirteen.
At first glance, Metallo is so much like the Terminator that he seems almost derivative. Yes, he has a kryptonite power core that makes him one of Superman's most consistently deadly foes, but he's still a powerful skeleton-like robot with cloned human tissue for skin. You have to wonder how they get away with it... until you realize that Metallo's first appearance predates the Terminator by almost three decades. He's often one of the first members of Superman's rogues gallery used in almost any telling of his story, because he's such a simple straightforward concept and is incredibly impactful. Very few other characters provide their particular hero such a specific, damgerous challenge.
Metallo's Comic History
A character named Metallo first appeared all the way back in the Golden Age fighting Superman: a scientist that wore metallic power armor. This power armored character saw a resurgence in the 2009 series Superman: Secret Origins as part of the origin story of a reimagined Metallo, as the character originally wore the suit before he was injured into a part man, part machine.
The long-standing version of the character as he is normally depicted debuted in 1959. This is where his normal origins as a criminal who was struck by a car and rebuilt into a Kryptonite-powered terminator were introduced. His robotic resurection came at the hands of a Doctor Vale, originally an act of altruism, although a later version of the scientist written by John Byrne depicted him as being a believer that Superman was the first of wave an an alien invasion (although it didn't matter too much, since Metallo quickly killed the Doctor in almost every version of the story).
Later appearances of the character featured his ability to rebuild himself using available machinery, like his appearance in the Batman Superman arc Public Enemies, when he replaced an arm with a backhoe scoop. He was even able to build himself to nearly skyscraper-size during the Action Comics arc Supergirls.
Our Metallo Story
We followed the traditional origin story for Metallo, but made a slight shift in who actually did the deed, taking John Corbens brain and putting it into the body of a proto-terminator. It just seems like such an obvious mad scientist thing to do, so we went to our resident mad-scientist organization S.H.A.D.E. THis sort of monster building for fun and profit just seems totally in their wheelhouse. we also stole a little bit from the Superman Animated Series, by making his original core uranium, and having him steal his kryptonian heart for lexcorp and installing it himself.
Corben has had a few upgrades over the years, like his ability to alter his shape into different weapons, or even increase his size, but most of these came from Neron (DC's Satan alegory) in exchange for his soul in an arc where many classic villains were likewise upgraded. We're not using that, so instead we gave him a few upgrades by various sources. One is the US Government thanks to classic jerk Wade Elling, but the second is actually Brainiac, which explains some of his more outlandish abilities thanks to the inclusion of alien technology.
His last story in our arc is a retelling of Action Comics 'Supergirls', a story that introduced three new superheroines. Metallo gets so powerful in that story that it's kind of rediculous, so hopefully by the end of our version he won't be able to access QUITE that level of power. It was a fun one-off, but the character makes more sense as a human-sized robot killing machine.