Seems like a cop-out to me. Bands like Napalm Death and Repulsion always cited Celtic Frost, Venom, Sodom, Slayer etc as much as they cited Discharge, Minor Threat etc. But you can only get so far through influences. I'm more interested in a reason, stylistically/structurally, why grind does or does not fall within the definition of metal. Particularly bands that use predominantly blastbeats would seem to me to fall within metal, because in contrast punk has always predominantly relied on fast rock rhythms.