I don't know exactly what your tastes are, but mine are pretty much all over the place. I just like music...good music in whatever form...I rank musicianship and songwriting above and beyond the genre...either it strikes a chord (pun intended) or it doesn't. Some of mine may be a bit more mellow than you hard-core metalheads (I dig metal too), but I think they are all worth a listen. Here are some (mostly) newer bands that I like (especially while driving):
Queens of the Stoneage (especially "Songs for the Deaf"!!!...must have...Dave Grohl

on drums)
...and you will know us by the trail of dead - "Source Tags and Codes"
The Strokes
Coldplay (for those early evening cruises with your woman next to you and the top down...great musicianship)
The Fray (see Coldplay)
The Dandy Warhols - "Welcome to the Monkeyhouse" freaky fun music
The Brian Jonestown Massacre - retro-sounding, pretty good stuff...free downloads on their site...just Google it
Franz Ferdinand has a distinctive sound, but I haven't listened to much of their stuff yet.
Nickelback
Smashing Pumpkins (90s...but you didn't mention them...you probably already have their stuff if your collection is as extensive as you say)
Gotta have some Pink Floyd on standby (I know...60s-90s...etc...)
Must have Dylan and Cream in your older stash somewhere...(yeah yeah...I know...it's probably already there anyway)
Radiohead
Wilco - especially "Yankee, Hotel, Foxtrot"
Foo Fighters - must have...from 90s to current...it's all good
Shawn Mullins (folksy...acoustic singer/songwriter) when I'm in the mood for mellowing out. (90s)
White Stripes
The Vines
Silversun Pickups - just checking them out...hear their sound compared to Smashing Pumpkins (Gish/Siamese Dream era stuff)