Well, if you wanna build speed and technique, practice practice practice. Both are key parts of metal guitar. Somebody already mentioned
http://ultimate-guitar.com/. The lessons on there are pretty helpful. Read up on proper picking technique there, picking is so simple but so important and often overlooked by beginners. Here a few articles on technique that I think are really good to read:
http://ultimate-guitar.com/lessons/...th_as_a_guitarist_vertical_or_horizontal.html
http://ultimate-guitar.com/lessons/correct_practice/finding_the_incredible_lightness.html
You have to minimize your motions as much as possible to play fast. Notice how when you see a good guitarist playing fast, there is very little movement in their hands. Their motions are slight and precise. You shouldn't be straining yourself at all while you minimize your hand motions. The key is to relax your hands, if feels backwards at first but it will become natural over time. If you don't do this stuff, you'll notice that it's hard to play fast cleanly and it will wear you out. If you do it right and take the time to refine your techniques, it will be effortless with practice.
Always practice with a metronome. When you're learning a lick or a scale or whatever, start at a low tempo. Choose a tempo that you can play perfectly at without making any mistakes. I usually start at 60bps. After I've spent a few minutes nailing the lick at that tempo and my hand motions feel natural and smooth, I bump it up by 5bps and play at that for a few minutes. I continue this until I reach a good speed. After I get up to about 144bps I take a break, because by then it's been at least an hour--often 2-4 hours. Remember, avoid straining yourself. Later in the day or during the next day, I'll come back into the same lick at 120bps. It's always much easier the second time around, I can usually go right up to 155bps if I've warmed up. From there I continue until I'm satisfied, which is usually at about 180bps. Who needs to play 16th notes much faster than that?
It will probably take you much longer to get your speed up, so don't try to force it. If you force it, you will reach a point where you can't go any faster. It will happen at a slower tempo than you think and you will be sloppy. You can never progress too slowly, but you can always progress too quickly. You have to learn to use specific muscles in new ways, it takes time. Always warming up before you play helps. Ultimate-guitar has plenty of warm-ups scattered throughout the lessons section.
You should take the time to learn all 7 modes of the major, minor, melodic minor, harmonic minor, and harmonic major scales. Those are all commonly used in metal and they will serve as building blocks for you to construct complex note progressions. There is an awesome book series called The Guitar Grimoire. There's one on scales, one on chords, and then one on progressions. All you really need is the scales one, since it has the chords in it too and it will teach you which chord shapes work with what scale in what mode and what key. The front of the book will teach you basic musical theory while it teaches you the scales I mentioned and many more. It's a great book, I've had it for 4 years now and I'm still learning new things from it.
Master palm muting, string skipping, alternate picking, hammer-ons/pull-offs, arpeggios, tremolo picking, and pinch harmonics. They are all common place in metal. You can find lessons for all of these techniques on ultimate-guitar.
Remember, practice is the key. It takes a long time to learn to play metal and do it well. Many try, but far less have the will and dedication to play metal skillfully. It's a very fast, technical, and musically complex style of music. It will most likely take
years before you get good at it, there's a lot to learn. Good luck man! It's worth the time and effort if you see it through.
