The Jane Eyre actor spoke to NPR about the highly-anticipated superhero prequel X-Men: First Class, in which he plays Erik Lensherr/Magneto.
"I was looking to do a studio film," said Fassbender. "What really intrigued me about this particular one was that you're dealing with the villain, if you like, in the piece as somebody that's very ambivalent and there's a lot of complexity to him. And there is cause for his feelings and his actions. Whether or not you agree with them is another thing."
The 34-year-old went on to state that he often relies on biographies in order to understand the backstory of a character.
"If there isn't a biography available that's my job to go away and write it. And what was great about [X-Men: First Class] is there was just such a wealth of information. I mean, I was really spoiled," he added.
X-Men: First Class also stars James McAvoy, January Jones, Nicholas Hoult and Jennifer Lawrence. Set in the 1960s, the film finds Charles Xavier (McAvoy) starting a school for mutants with his future enemy Erik Lensherr (Fassbender).
McAvoy recently revealed that nobody recognises him, stating that he is rarely approached by fans when he goes out.
X-Men: First Class opens in cinemas in the UK on June 1 and the US on June 3.
>'X-Men: First Class': Pictures
Watch the trailer for X-Men: First Class below: