The 37-year-old actress shocked fans with a surprise appearance at the anticipated movie's Los Angeles premiere on Monday, over five years after she last starred as scientist Jane Foster, Thor's Earth-born love interest Thor: The Dark World (she also appeared in 2011's Thor).
"It's so fun to get to part of that universe," Portman said, lighting up while speaking to ET's Katie Krause at WE Day California at The Forum in Inglewood, California, on Thursday. "I'm very excited for the film to come out."
WE Day California, the world's largest youth empowerment event, celebrates doing social good -- and the actress couldn't have been more proud to be a part of it.
"I was lucky enough to travel to Kenya with the WE foundation several years ago and was just so impressed by the work they do," she said. "And then to see the work that they do here, both in the U.S. and Canada, in Japan, with students who are wanting to make change and empowering them and giving them voice and rewarding them [is great]."
"[They are] making it like, a cultural movement that this generation is going to be socially active and going to make change. I'm just very inspired by all the young people here today," Portman added.
WE Day California will air on Aug. 9 at 8 p.m. ET/ 7 p.m. PT on ABC. See more from the event in the video below.