Green previously starred in TV's "Beverly Hills, 90210" and "Terminator: The Sarah Connor Chronicles."
"It's an unwelcome one," Green told TVGuide.com of his character John Corbin's change into Metallo in Friday's episode.
"It's not something that he asks for," Green added. "As you see, the man steps off a curb and wakes up being who he is. There's a part of him that enjoys it and realizes that he can use it to the best of his abilities and use it to accomplish what he wants, but at the same time, it's probably not the happiest thing being Kryptonite-powered and robotic. It's not what he asked for, and I think there's a lot of anger that comes with that."