'Love the Way You Lie,' Eminem's weighty duet with Rihanna, which explored a crumbling and destructive relationship, was one of the biggest hits of both of their careers. It makes sense for them to reprise with 'The Monster,' which will appear on his 'The Marshall Mathers LP 2' and is a much more upbeat and less serious track, sonically speaking. It's not nearly as powerful or affective as the previous partnership, but it's not supposed to be.

While the song does address mental health issues -- essentially, the rapper and the topless wonder of the world admit to being bonkers -- it isn't melancholic. Em and Ri sing about OCD, the voices in their heads and more. While the song is lighthearted, their attitudes really are not. It's as if they're saying (and rapping and singing) that it's okay to be cray cray.

Rihanna's icy voice delivers the intro and the choruses, while Em pops off rhymes in the verses, with his trademark nasally style. "Everything that I love is killing me / And I can't conquer it" is one of his most poignant lines, while RiRi sings about being friends with the monster under her bed. But when Em sings about being crazy, we can't help but wonder if the monsters they sing about are really just the darker sides of themselves.

There is some vulnerability in the lyrics and some poppy synths sprinkled at the end of the choruses, but the whole song leads up to the final 30 seconds, which build up to a harmony and a fade out.

Em and Ri have undeniable vocal chemistry and it asserts itself on 'Monster.' This song has nothing to do with goblins and ghouls, unless, of course, they're of the mental sort.

Listen to Eminem, 'Monster' Feat. Rihanna