ET's Lauren Zima spoke with the actress at the event's red carpet in Beverly Hills, California, where she reflected on her impressive career, which included playing "a lot of wives and a lot of girlfriends" before she was able to break the mold with 2003's Monster.
"I mean, it's hard -- they really are like your children. But I think Monster was definitely a moment in my career where I realized the opportunity that I was given was a chance to show that I was capable of more and it did change my career," Theron said of the film, in which she played real-life sex worker-turned serial killer, Aileen Wuornos. The role earned her an Oscar for Best Actress in 2004.
"After that, I didn't have to fight so hard for those interesting parts anymore, and more opportunities came my way to get outside of my comfort zone and do things that were maybe not expected for me," she continued. "I think from that moment on, I built a career that has kind of defined what I really wanted my career to be -- not typecast, not stereotypical roles, but to really do things that are interesting and challenges the psyche of how we look at people."
Theron remembers being put into a bit of a box before her total transformation for the Patty Jenkins-directed film. "I think we all get labeled, and I played a lot of wives and a lot of girlfriends. And then after that, I got to play people who were going through serious things, and it was just more interesting," she explained.
Two years after Monster, Theron was nominated for another Academy Award for her role in North Country. She's since starred in everything from blockbusters to dramas to romantic comedies -- and jokes her kids have seen the full spectrum.
"They've seen Prometheus, Monster... I'm trying to think of other R-rated films," she said with a laugh. "I started with the good stuff. I just feel like I want their level of taste to be challenged."
"No, they see all the kids movies I've done. They really like this movie I did a long time ago called Mighty Joe Young. They're finally -- they go, 'We want to see the big monkey.' I'm like, 'It's an ape.'"
Theron is "not going anywhere" anytime soon.
"I mean, I thought of it as just like, my career up to now," she told ET of being honored with a career achievement award at such a young age. "No, I'm not going anywhere, sorry guys! I've only begun."
"Listen, I'm always like, 'Somebody made a mistake!' So, let's not talk about it too much before somebody's like, 'Wait a second, she should not be getting this career achievement award,'" the actress joked.