Grindcore isn't punk or metal. It is Grindcore. Grindcore takes elements from the metal and hardcore/punk genres. the "core" in grindcore comes from "hardcore", which is essentially punk derived. Technical Deathmetal with grind influences is commonly "Deathgrind"... deeds of flesh, origin, pyameia, etc... It all sounds metal, as people have brought up earlier in the thread. But there defintiely are key distinctions and influences coming from alot of musical areas. For example, Soilent Green play deathmetal/grindcore with even some southern rock influences. If you listen to Brutal Truth and older Napalm Death/ Carcass, you can hear the punk influences at work. Particularly in the lyrical content, the extremely speed up punk riffs. Back then, punk/grind/crust etc were all a united scene. One ultimate example of complete punk Grindore would have to be Extreme Noise Terror.