Machine Gun Kelly Says He'll 'Always Collaborate' with Fiancée and Good Mourning Costar Megan Fox

Machine Gun Kelly and Megan Fox are in for the long haul.

The couple attended the premiere of their new film Good Mourning on Thursday evening at the London Hotel in West Hollywood, California.

For the night out, Kelly, 32, and Fox, 35, matched in complementary pink ensembles while walking the red carpet.

Fox wore a sparkly pink strapless Philosophy di Lorenzo Serafini gown with a thigh-high slit, which she accessorized with a pair of similarly colored platform heels.

Kelly, meanwhile, sported a pink satin Dolce & Gabbana suit that featured a red rose pattern all over. The rocker even smoked a joint as he walked the red carpet.

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RELATED: See Machine Gun Kelly, Megan Fox, Pete Davidson, and Mod Sun in First Trailer for Good Mourning

Good Mourning follows Kelly's London Clash, a character who is forced to choose between pursuing true love or a once-in-a-lifetime movie role.

In addition to starring in the film, Kelly also serves as writer and director alongside friend Mod Sun, who co-wrote and co-directed the film.

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Pete Davidson, Dove Cameron, Becky G, Whitney Cummings, Zach Villa and Jenna Boyd round out the cast.

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Speaking with PEOPLE at the premiere event, Kelly said that directing his fiancée in the film was a collaboration between both stars.

"She didn't let me lead her character too much in any direction. She was like 'I got this. I understand what this character is,' " he explained. "She improvised and brought [her character] Kennedy to life, and I've heard a lot of people say that that's their favorite character in the movie."

"I'll always collaborate with Megan," the Mainstream Sellout musician added. "I'm madly in love with her — and I'm also a fan."

RELATED VIDEO: Machine Gun Kelly Designed Megan Fox's Engagement Ring to Represent Their Unique Relationship

Kelly also reflected on his favorite part of shooting the film with his soon-to-be wife, telling PEOPLE that many of Fox's lines were inspired by their actual life together.

"Every line that people wanted to keep in the editing station that she had said was stuff that she actually had said to me in real life," he detailed. "She was like, 'You're 30. It's time to grow up.' "

Starring in the movie, Kelly added, also allows himself to show audiences another side of himself.

"I think there's a Machine Gun Kelly persona that people have married themselves to, and the character that I play in the movie, London, is a vulnerable humanized version of who I really am," he said.

Good Mourning hits theaters and will be available on-demand May 20.