The nominees for the 2015 Grammy’s have officially been announced. Artists in the metal category include Slipknot, Anthrax, Motorhead and more. Here’s a list of all the metal/rock artists nominated this time around: Anthrax – “Neon Knights” (Black Sabbath cover) Mastodon – “High Road” Motörhead – “Heartbreaker” Slipknot – “The Negative One” Tenacious D –…