Michael Shannon has quietly become one of the most interesting and original actors of his era. Climbing a ladder of indie gems, he’s established himself as the natural heir to Christopher Walken, but with a jolt of broad-shouldered menace. He can take your head off in roles as diverse as Ashley Judd’s deranged lover in “Bug” or glam-rock enfant terrible Kim Fowley in “The Runaways.”

The trade paper the Hollywood Reporter says there is “possibly no more mesmerizing American actor.” Now, 20 years into his career, he’s about to go nova thanks to a trifecta of spine-chilling roles. He stars as Golem-like mafia killer Richard Kuklinski in “The Iceman.” He’s about to appear as snarling General Zod in “Man of Steel.” And he’s all over the Internet with his hilarious interpretation of a sorority girl’s e-mail rant.

In a recent phone conversation Shannon said the key to playing lost souls is uncovering their humanity. “That’s my job,” he said. “Their spirits are kind of under rocks. It’s my job to try and illuminate them. Lift the rock off and show what’s underneath, you know? A lot of the world doesn’t see that humanity.” Watching the interviews Kuklinski did for two HBO true-crime specials on his horrific career, “I saw a man who’s suffered a great deal and is in a lot of pain.”

Kuklinski and his brother were physically abused by their father; another brother died after what the parents called an accidental fall. In response, Shannon said, “he learned he had to defend himself. And he took it to an exorbitant degree and became the aggressor.” As a mob killer, he was implicated in more than 100 murders, getting up to $50,000 each. Yet his family and suburban neighbors never suspected Kuklinski was anything other than the successful businessman he claimed to be.

“A lot of people ask me why I wanted to do this picture, why I wanted to play this guy,” who funds an ostensibly perfect family life with dirty deeds. “Kuklinski’s an exaggerated version of a lot of people, actually. People who do things that have detrimental effects on other people to make money. They know that while they’re doing it. They do it anyway and take a paycheck. Then they go home to their families. Did I do this movie because it’s a mob thing, I get to wear fancy clothes and act like a badass? No, I did it because it’s a parable, a story that’s important for people to see right now.”

Shannon stepped into acting as a release from an unsettled childhood. He was born in Kentucky in 1974 to a lawyer mother and accounting professor father who split up soon after; each parent has been married five times. At school, he was troublesome enough to be referred to a psychiatrist, whose office he ravaged and therapy he rebuffed, though they have since become friends.

Living in Chicago with his father, he aspired to two great Chicago professions, architecture and jazz, before settling on a third, acting with the Steppenwolf Theatre Company. As Superman’s nemesis in “Man of Steel,” he seems set to join the ranks of Steppenwolf alumni John Malkovich, Nick Offerman and William Petersen.

“I’ve seen the movie and it’s stunning, a work of art,” he said. While Shannon plays another heavy, it’s a unique addition to his vivid portrait gallery. “General Zod is very different for me and very different from what Terence Stamp did. I remember seeing the movie when I was a kid, being completely blown away by him. But I’m not going to impersonate him. That would be ridiculous.”