I think metal has different meanings to different folks, but I'm in 100% agreement that bands like Godsmack or Disturbed are not true metal. Not saying there's anything wrong with that style of music, but it's not metal (in fact if you notice most every song from both of those bands seems to be only 1 chord with a slight variation here and there...on track 7 you're like 'haven't I heard this track already?..perhaps twice?').

For me, since I'm old (almost 37) one of the major albums that defines metal, which also inspired me to play guitar, is Master of Puppets. So old school bands like older Metallica (funny how we all have to specify older Metallica), Megadeth, Maiden, Slayer, Priest are metal and paved the way for newer, what I consider true metal bands, like Killswitch, As I Lay Dying, Evergrey (one of my favs), Mercenary, Before the Dawn, Scar Symmetry and such. But there's also a lot of metal sub-genres (progressive, gothic, ppwer, melodic, etc) and some bands in those realms can be questionable. Like Nightwish or Within Temptation...those could be leaning more towards the gothic rock side but are often labeled as metal (more so Nightwish). And bands like Dream Theater and Darkwater (both great bands) aren't as heavy as most of the metal bands out there but are still deemed as progressive metal bands (and rightfully so due to their complex riffs).

I think metal will constantly evolve but true metal will still maintain it's core roots and 'values' so to speak! It will always be heavy and will capture those of us who don't care for what mainstream society is pushing. Our love for metal is something deep within, almost unexplainable. I'm glad metal has expanded despite the fact a lot of us don't care for some of the sub-genres (ex: nu-metal, which I don't consider true metal either...should've been nu-rock instead). But if you notice, those bands and genres usually don't last too long; they fizzle out over time and we're left with our true metal, old and new, which will always remain.