Grunge was influenced by metal and was a fusion of hardrock, metal and punk, so naturally one could say it sounds like hardrock or metal. However when grunge came around, that is when Nirvana, Alice in Chains, Sound Garden and Pearl Jam came to national awareness.... it was a totally new sound, nothing like any of the pop metal, heavy metal or old hardrock we were accustomed to.... it was new and the term Grunge fit it perfectly because it was grungy, not articulate, choppy and fast like that of metal.
I know I mentioned it before but they opened for at least part of the VanHalen "FUCK" tour, which I attended the local concert. I knew I was listening to a new sound, a new wave of music that was going to take hold. I enjoyed it but the VanHalen fans around me were not impressed and were becoming very impatient.