A riffing style popularized by legendary Metallica frontman James Hetfield. It is basically a punk-rock style rhythm meets Motorhead/NWOBHM etc (new Wave Of British Heavy Metal) resulting in a potent machine-gun gallop sounding orgasmic tune to what most Metalhead calls now as Thrash. Their milestone debut album "Kill 'Em All" introduced that kind of sound and after that it literally spawned hundreds of Thrash bands mimicing that style.
"Metallica single-handedly patented and perfected the Metalli-crunch, that's why they became a legend to the music world"
by TT Boy4 April 12, 2010