PIC: Megan Fox Kisses Another Guy!

Credit: Eric Ford/On Location News; Frank Micelotta/Getty Images; Kevin Parry/WireImage.com

Megan Fox locked lips with Lost alum Dominic Monaghan Friday in L.A.

No, the newlywed wasn't cheating on new husband Brian Austin Green.

She was just shooting a cameo in Eminem's upcoming video "Love The Way You Lie."

E! News reports that their roles are inspired by Eminem's relationship with ex-wife Kim (whom he married and divorced twice).

"Things start off with a sex scene between Megan and Dominic," a source tells E!. "Then they fight but end up having sex again."

The source says the video (directed by Joseph Kahn) -- which also reportedly stars Rihanna -- is "gritty" with "lots of passion."