revealed that Corben's change of heart happened due to his biology rejecting the red kryptonite heart and him becoming a mercenary. During this time, he was tasked by a tyrannical dictatorship to subdue and eliminate the rebel forces' protector: a Kryptonite powered Lana Lang. Toyman gave him his new green kryptonite heart as well as the ability to absorb meteor energy signatures to strengthen himself. After absorbing Lang's Kryptonite-powered nanites, Corben gains the ability to assimilate metallic or mechanical constructs. After Lang and Lane remove his power source, the U.S. government defeats and incarcerates Corben. Arrowverse Six different incarnations of Metallo appear in live-action media set in the Arrowverse: John Corben appears in the Supergirl TV series episode "The Adventures of Supergirl", portrayed by Frederick Schmidt. He is initially hired by the then-arrested Lex Luthor to assassinate his half-sister Lena Luthor to prevent her from rebranding LuthorCorp, but Corben's first two attempts fail due to Supergirl and Superman's intervention. During his third attempt, Corben is foiled by Lena and Alex Danvers, with the former shooting him after he takes the latter hostage. While being sent to the hospital, Corben is intercepted by Project Cadmus, who convert him into the first Metallo. After meeting Project Cadmus' leader, later revealed to be Lex's mother Lillian Luthor, Corben fights Supergirl and Superman alongside another Metallo (see below), with Supergirl and Danvers defeating Corben by removing his power source. Corben is sent to jail, but Hank Henshaw smuggles in an artificial Kryptonite "heart" to help him break out of jail and frames Lillian for it. Due to the artificial Kryptonite's instability however, Corben slowly undergoes a radiological meltdown and ultimately self-destructs despite Supergirl's best efforts. To assist Corben, Lillian converts unwilling Project Cadmus scientist, Dr. Gilcrist (portrayed by Rich Ting), into a second Metallo. During his fight with Superman, the Martian Manhunter removes Dr. Gilcrist's Kryptonite heart, deactivating him. An alternate universe incarnation of Metallo appears in the four-part crossover "Crisis on Earth-X", voiced by Frederick Schmidt. This version is an automaton used by the Nazi regime of Earth-X, who use Metallo to take several of Earth-1's heroes captive. It is eventually destroyed by the combined efforts of the Flash, Black Canary, Killer Frost, Citizen Cold, the Ray, the Atom, Firestorm, Heat Wave, Zari Tomaz, Vibe, and Vixen. The fourth incarnation of Metallo appears in the fourth season of Supergirl. Introduced in the season