"I'm asking them to go from zero to 100 in two seconds," the director of the "Love the Way You Lie" video told MTV News, "so they were using all their techniques as actors."
In the video, Fox and Monaghan play two a troubled couple that alternates between scenes of domestic intimacy to instances of jarring violence. The song is a collaboration by Eminem and Rihanna about abusive relationships.
"Dom would be calling her names, she'd be calling him names," Kahn said. "To see them turn it on like that, it was really a fascinating acting study."
With Fox and Monaghan only available on set for 2 days, shooting took place at a light-speed pace. "You're going to have to ramp up into emotions in two seconds," Kahn told his actors.
The directing team initially was not sure they could land a big name like Megan Fox, star of "Transformers" and "Jonah Hex."
"I just thought, 'why don't I try this?'" Kahn said. "I mean, we have the biggest artist in the world, with the hottest song on the planet, with the hottest female artist. And it's a meaty role."
He said it turns out Megan Fox is a fan of Eminem's music, and she agreed to make the video.
Kahn said that although there are some parallels between the theme of the video and Rihanna's personal life, fans should not look too deeply to connect the dots.
"Obviosly there are parallels between in terms of the song, with Eminem's personal life and Rihanna's personal life," the director said. "But ultimately, if you really look at the video, its not about anybody in particular. It's a story about two characters I created."