Rick Rubin has collaborated with AC/DC , Johnny Cash , Justin Timberlake and Metallica .
Rubin has also worked with artists from other genres such as AC/DC , Johnny Cash , Justin Timberlake and Metallica , amongst othersIn 2007 , MTV called him `` the most important producer of the last 20 years '' , What 's Up With That Bearded Guy From The '99 Problems ' Video ? –
Rick Rubin