Good point, Deadite. That is why I have personally decided to limit how much bands I listen to: quality rather then quantity.
As a former music theory student myself, I believe my blue print would be tab and music sheet. I wrote awhile ago that tabs should not be discredited as they have the music tradition in the French, Italian, German, and Welsh vernacular.
A basic movement of any standard piece is for instance, is G-C-D. What notes are there in a G major chord while in G major scale? 1-3-5 ( G B D). There is one sharp, the F sharp. The opposing minor scale would be E minor.
When we know what notes are in a scale, and what forms a chord, we can then make movement in that scale by using harmony which you then can use, counterpoint or a bass pedal. (this being I would pluck a G note in a steady beat with one instrument while making a movement with the other, G C D C D...)
This is why I can never wrote any of my music for just one guitar and play live. When I play live I use at least one guitar backing track while playing the other live. This modus operandi has stuck with me for these many years.
Now, apply this to metal, we can then say how we can get that sound which makes it metal(not by tone alone as this is a different subject) we can harmony any of the riffs with thirds minor thirds fourths and the augmented and diminished chords.
In the G major scale that is our example:
Gmaj Amin Bmin Cmaj Dmaj Emin F# dim
The Amin, Bmin, Emin and F#dim chords would be great to use in this scale to get that harsh wicked and unghastly tone. In this case, a music tone and not the above mentioned sound.
In the follow example I have made, the left guitar will play a Amin chord to a Bmin chord, while the right guitar will play a Emin to a F#dim. Since each chord is struck twice before moving, I can then have that F#dim strike the minor third in the first strike then during the second strike, I use the diminished chord(1-b5).
I am still in G major, but now I am utilizing the "darker" parts of the scale to full effect:http://www.youtube.com/watch?v=hmFaHi3or_o