Exodus was founded in 1979 by guitarists Kirk Hammett and Tim Agnello, drummer Tom Hunting, and vocalist Keith Stewart. Hammett famously left the band in 1983 to go join Metallica after they split with Dave Mustaine, and was eventually replaced by guitarist Rick Hunolt.
Metallica went on to release their debut album Kill 'Em All in 1983, while Exodus released their (eternally underrated) thrash classic Bonded By Blood in 1985… but what would've happened if Hammett stayed in Exodus? Apparently they'd have some of those sweet Kill 'Em All riffs.
In an interview with Metal Hammer (via Guitar.com), Hammett noted that he felt less bad about taking his riffs over to Metallica than he did about leaving his longtime friends in Exodus.
"The [riffs] came from songs that I had written, music that I had written," said Hammett. "I consider them my parts. I didn't feel guilty about that, but I did feel guilty about leaving the band I started in high school.
"I have known [Exodus drummer] Tom Hunting since I was 16 years old, I've known [Exodus guitarist] Gary Holt since I was 17. We're all close to this day, but there was a lot of guilt there for a while. A little bit of remorse. But I really felt that Metallica was my calling. I feel more comfortable playing in Metallica than I ever did in Exodus, so go figure."
It's especially interesting for Hammett to make these comments considering he was never credited as a songwriter on Kill 'Em All. The album was credited as being written by frontman James Hetfield and drummer Lars Ulrich, with Mustaine receiving credits for "The Four Horsemen", "Jump In The Fire", "Phantom Lord", and "Metal Militia". And then obviously "(Anesthesia) – Pulling Teeth" was all the majesty of Cliff Burton alone.