Charlize Theron brought boyfriend Sean Penn as her plus one to the film premiere for A Million Ways to Die in the West in Westwood, Calif., on Thursday, May 15 Credit: Jason Merritt/Getty Images

Supportive Sean! Charlize Theron and boyfriend Sean Penn stepped out to attend the actress' film premiere for A Million Ways to Die in the West in Westwood, Calif., on Thursday, May 15. Click here to see more pics of the couple.

All eyes were on Theron, 38, who looked stunning in a black lace knee-length dress on the red carpet. She topped off the old Hollywood look with matching heels and added a hint of bright color with a bold red lip. She walked hand-in-hand with Penn, 53, and took time to pose with her co-star Seth MacFarlane.

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The Dark Places star recently returned to the West Coast after making several appearances in New York City. On May 5, Theron and Penn showed their affection for each other as they attended the Metropolitan Museum of Art's Costume Institute Gala.

"They play fought with each other," a source told Us of the pair's shenanigans at the star-studded afterparty at the Standard Hotel's Boom Boom Room, which also served Budweiser. They started "rigorously making out" after she was seen playfully "biting on his neck." 

The happy couple stuck around for a few days while Theron took over hosting duties on Saturday Night Live on May 10. "She's a keeper, that's for sure," Penn told Piers Morgan back in January, according to a blog written by the British TV personality. "I'll do my best to keep her anyway!'"