Robb Flynn goes way back with Slipknot. His band, Machine Head, toured with the infamous Iowan mad men multiple times, including on one of the 'Knot's earliest North American runs, in 1999 with Coal Chamber headlining. Flynn also joined Slipknot's original drummer Joey Jordison as one of the main songwriters on the 2005 Roadrunner United project, and collaborated with the band's singer, Corey Taylor, on the song "The Rich Man." His personal history with the group gives him a deep connection to their music and, in particular, one especially vitriolic cut off Slipknot's 2001 sophomore offering Iowa.
I heard this for the first time at Slipknot's studio. They were in mixing [Iowa], ripping my face off with the volume turned up to 11. This song makes me want to run and jump feet first into people's chests, smash them to the ground, then stand on top of them laughing maniacally. [Laughs] It warms my soul to hear a man that angry!