The cover song. Before many acts got their big break, they started somewhere playing covers before eventually growing their catalog to include original material. For some acts like Disturbed and Foo Fighters, covers have remained a favorite spot in their live shows to this day.

Other acts such as Limp Bizkit and Red Hot Chili Peppers have taken things a step further, making their covers sound something uniquely their own. Buckcherry even went so far as to change a song title to fit their aesthetic, but kept the basic attitude, sentiment and most of the lyrics of Icona Pop's "I Love It" in their newly titled "Say Fuck It."

Sometimes, a cover can put a spotlight on a song that might not be as familiar to a modern day generation, like Alter Bridge has done bringing recognition to Robert Johnson and AC/DC did reviving an oft-covered track from the Joe Williams’ Washboard Blues Singers.

We've picked out 40 of the biggest rock acts covered by Loudwire, scanned over their recorded and live histories and offered our takes on the best cover song for each of these bands. For some, the picks were quite simple given the immense popularity of one cover or the lack of depth in a band's covers catalog. For others, there are some that will likely be the source of great debate with bands offering proper respects to more than one song in equally beloved fashion.

So join us as we revisit the best cover songs of 40 top rock acts.