Like Maiden or early Metallica without vocals?
Well, a lot depends on your definition of “metal.”
The only guy I can think of specializes in hard rock instrumentals is Joe Satriani. I liked “The Extremist” a lot. But if you’re looking for the equivalent of Metallica or Iron Maiden, Satriani may seem a little too mellow to you,
I would recommend Praxis’ “Transmutation”. It’s not exactly metal but it features Buckethead on guitar and is rather heavy and sounds great at top volume.
Does Apocalyptica count?
Apocalyptica does some REALLY good things. It’s mostly covers, but it’s good. I love their versions of Master of Puppets and One.
They’re probably responsible for Metallica doing S&M.
I’d go with anything by Joe Satriani. You might try some Steve Morse – he’s not metal but he has the hard, loud guitar tone and he rocks. Also Vinnie Moore’s stuff is metal, but it relies on a lot of sweep-picking and crosspicking and is IMHO way too fast to be enjoyable.
Well, I made an instrumental CD by ripping a bunch of Metallica songs and cutting out the vocals with CoolEdit. I’d post the mp3s to Au*Gaxy, but the band would probably sue me if I did. 
You might wanna try out Marty Friedman (ex-Megadeth guitarist) or Liquid Tension Experiment (Dream Theater side project). Although the LTE stuff tends to have a lot of wank.
Does that work well? Is it hard to do? Sorry to hijack I have just been wondering about that.
Try Anacrusis. They’re a little like Rush but more metal.
Well, entire albums w/o vocals is tough. The guitar “gods” (Joe Satriani, Steve Vai, Michael Schenker, Yngwie Malmsteen) do have several instrumental albums between them.
Chris Poland made a Megdeth-ish cd called Return to Metalopolis. Its not bad.
There are two bands who do use vocals but also have many long brooding instrumental songs/ passages.
Opeth have very long songs, I suggest any of their albums - Still Life, Orchid, Blackwater Park, or Morningrise. Beware some harsh vox mixed in there.
Green Carnationp - Light of Day, Day of Darkness. This is a concept album which contains only one hour long song. There are various vocals including a choir but the spirit of the album is in the instruments. You can check out a 7-minute sample here. Click on “enter” and then “MP3” at the top of the flash presentation.
Thank you all for your suggestions. It doesn’t look like what I am looking for is out there. The closest I have found is a band called patriarch on mp3.com and they only have one song.
How about a guy named Jason Becker?
He’s a guitarist who was of the same caliber as Steve Vai, in fact he was offered the job of David Lee Roth’s touring guitarist in the late '80’s, but shortly thereafter was diagnosed with ALS (Lou Gherig’s Disease). He’s still alive, but now confined to a wheelchair and unable to play his guitar anymore.
Check out his album “Perpetual Burn.” It’s kind of a shred record, but theres a lot of loud, fast, technically intricate songs. It might be right up your alley. Prior to that he collaborated with Marty Friedman (later of Megadeth) under the name Cacophony and released a couple albums. But some of those songs have vocals.
Still I recommend Jason Becker. Also, if you can download a video of him playing Paganini’s 5th Caprice, get ready for your jaw to hit the floor.
Go old skool: Yngwie Malmsteen - Rising Force. It’s not all instrumental but it’s definitely “metal”!
Another one that’s “not-metal-but-heavy” is Glenn Danzig’s Black Aria. It’s actually more orchestral than heavy metal (no screaming quitars) but it’s very good. Short too, only about 25 minutes long. Even if it’s not what you’re looking for, I recommend it.