Hardcore, metalcore, emocore... it's all the same to me.
9 times out of 10 I prefer actual singing to screaming, as well as a real melody rather than mindless thrashing. Oh, and songs over three minutes long.
And Metallica is still metal. Marylin Manson is still metal. To me, everything is metal first, subgenre second. Manson may be more industrial now, but he's still metal. And better than ever in my opinion. And St. Anger rubbed me the wrong way at first, but I gave it more listens and it really grew on me. It's rediculously heavy. Unconventional? - yes. Metal? - very much.
Personaly, I think Metallica's first two albums are highly overrated and I don't even like them anymore. Puppets, Justice, and Black Album makes a great trilogy of sorts. But for my money, they were never more polished and fined tuned than during the Load/Reload era. I absolutely loved that sound.