Oh, Penguin, I found a cool site where you can enter the band you like, and they'll give you suggestions of other bands that are similar, or that fans also like... here's the link http://www.pmbrowser.info/audioscrobbler.html

Have fun! I spent a lot time there

Just an example, when you type in Slipknot, you get dry kill logic, killswitch engage, american headcharge, nothing face, biohazard, motorhead, one minute silence, tool, rage against the machine, and many others...