Celtic Frost
Dave Grohl (ex-Nirvana, Foo Fighters) and Mark Tremonti (Alter Bridge, Creed) have both stated on several occasions that Celtic Frost were an influence. Grohl subsequently invited Celtic Frost singer Tom Gabriel Fischer to participate in the recordings of his 2004 solo project, "Probot", resulting in the co-written song "Big Sky". Alternative country singer Ryan Adams has also claimed influence from Celtic Frost, amongst many other metal bands.