can someone direct me towards some really heavy bands who lean mostly or all the way towards clean vocals?

ewwwwwwwww, clean vocals.

dunno of any to be honest. well, any good bands.

Fudge tunnel, nailbomb, sepultura, fear factory, acid bath, tool, sparta, trail of dead (they're more noisy but still awesome)

in that vein...

Chevelle?

I don't remember if they're good or not. I think they are.

Chevelle are awesome, keep em coming

those bands don't all have clean vocals.

you should check out anathema, katatonia, and opeth. fantastic bands, with clean vocals.

my metal years were mainly spent listening to: Exodus, Testament, Nuclear Assault, Anthrax, Slayer, Wrathchild America, Death Angel, and the like but with a heavy dose of Maiden, and some other random shit......

I'm not sure what you mean by clean. Like harmonies and shit or just not either growling or going falsetto all the time?

Amorphis -- I think there's one growled song on Tuonela, none on Am Universum nor ...erm...their last one, whatever it's called, Far from the Sun? Highly recommended -- this is one of my artists that I am constantly going back to. Ditto Katatonia's last three albums: Tonight's Decision, Last Fair Deal Gone Down and Viva Emptiness. And yes, more recent Anathema as well.

Neurosis is screamed -- not really that far off from something like Judas Priest, really, just a little harsher, quite tolerable. I consider it more real than most "growled" vocals, which I find laughable.

Devin Townsend's stuff is screamed, also, but again, quite melodically.

A lot of the proggier stuff -- Ayreon, Frameshift, Fates Warning, etc.

Opeth actually has quite a bit of growled vocals, except on that Damnation album, which was weird for them -- it's not even metal.

How about femme vox? Plenty in this area:

Peccatum
Nightwish
Sirenia
White Willow

Dillinger Escape Plan w/ Mike Patton - Irony Is A Dead Scene EP

if by clean vocals you mean not always screaming (although this still has plenty)

I rather like Million Dead. They usually get classified as a metal band but they sound a lot like At The Drive so I'm not sure if they actually are metal or not.

The new Mastodon -- Leviathan is fan friggin tastic...well new in 04.
Not as much screaming in music by -- In Flames.
Lacuna Coil is good, but not especially over the top technicians.

On a proggy note. Porcupine Tree -- In Absentia has heavy moments and all clean vocals.
Dream Theater, has some wanky screams occasionally but the music is undeniably technical genius.
Also if you like that sort of thing, DT, check out OSI (Office of Strategic Intelligence) , Liquid Tension Experiment.

And lest we forget, Muse has some heavy moments and all clean vocals.

Killswitch Engage. Pipes I tells ya.

one of the better U.S. bands that are obsessed with Gothenburg.

Though some of these lean more towards stoner or doom some of my favorites that I consider metal related:

Ufomammut - Snailking: Hard to describe, a mashup of Sleep at their spaciest and Kyuss at their heaviest,

5ive (5ive's Continuum Research Project) - s/t: The Hemophiliac Dream EP Instrumental rock, nothing but guitars and drums. Heavy swirling and weird, akin to Pelican but much more driving, heavy as hell too.

Sons Of Otis - Songs of Worship: Awesome album by an awesome overlooked band, they refer to themselves as space blues, their cover version of Hendrix' "In From the Storm," is pretty damned amazing.

Fu Manchu - anything before California Crossing The quintessential riff rock band, they are about as creative as AC/DC, but man can they rock, of special note are the early fuzzed out albums: In Search of..., Daredevil and Eatin' Dust.

Dozer - In the Tail of the Comet: Although they sound an awful lot like Kyuss, one listen to their debut should convince you they are an entirely different beast. Listen to the song "Supersoul" or "Riding the Machine" and prepared to be "rock"eted into stoner space.

Nebula - any album Made up of ex-Fu Manchu and Kyuss dudes, this is straight up stoner rock in the truest sense of the genre, nothing but riffs and spliffs for these guys, all fast cars, loud music and hard rockin. But seriously they are pretty damn good too. Close to High On Fire but a bit more spacey.

SunnO)))- This is gloom at it's finest. All nearly muted drums, swirling feedback, and frequencies so low that at times your teeth threaten to leave your jaw. Take everything clean about Isis and replace it with the eeriest samples of all time and you might get something close.

Khanate- These dudes play slow. Painfully slow. Distortion abounds and a legitimate metal voice rises. There's a ton of space between notes here but never a bit of silence. Just a killer doom band all around.

Uncertainty Principle- This might be the heaviest damn band of all time. They play beyond slow, I'm talking making SunO))) sound like some speed metal. Unlike SunnO))) however there is absolutely nothing organic here. To imagine that it is actually humans making this music is a task in itself. My favorite description I've ever heard of them is such, "This is what the universe will sound like in the last split second before all matter collapses back in on itself and the universe disappears into a point of absolute density." Good stuff to say the least.

Khanate is the shit.