Charlize Theron has said she likes playing evil characters because it is like getting “a free pass for your soul”.

The actress, who won an Oscar for her portrayal of serial killer Aileen Wuornos in Monster in 2003 and has played other onscreen villains, said she finds portraying sinister people “cathartic”.

She told W magazine: “Look, I’ve always been fascinated by abhorrent behaviour.

Charlize Theron
Charlize Theron (PA)

“I have a real interest in why people do horrible things.

“I read a lot of books and am fascinated by whether deviant behaviour is caused by nature or nurture.”

Theron, 41, said part of her “wants to understand that darkness, but I can’t really understand it”.

She said: “So, it is cathartic to play a character who is evil.

“It’s a free pass for your soul: Nothing bad is going to happen, and you can explore what it would be like to be in that skin.”