Eminem is a terrific guy to have on your album.

Just ask Pink. Her latest project Beautiful Trauma moved over 400K in its first week, in part because of the heavily promoted Eminem feature 'Revenge'.

But Black Sabbath guitarist and heavy metal legend Tony Iommi actually turned down the chance to feature Eminem on his 2000 solo debut, Iommi.

Shady reached out to Iommi and asked to be on the album. But Iommi said no because he didn't know who Em was. Mind you, this was about when The Slim Shady LP was making Eminem into a star.

The Foo Fighters' Dave Grohl, Smashing Pumpkins' Billy Corgan, Billy Idol and Iommi's Sabbath bandmate Ozzy Osburne were among the vocalists on the album.  Iommi even cut a track with another Detroit (then) rapper Kid Rock, but it didn't make Iommi's final cut.

Iommi peaked at 129th on the Billboard charts. So it looks like Tony could have used some Shady.

[Related: Eminem's album has a date.]