I record and mix random stuff using my gutiar and sound blaster live card. I say if you can EQ the sound coming out of your amp and into the reorder so you're not tweaking afterwards. For a solid metal sound boost the low end an the high end as most pickups as far as i can remember, i may be wrong, focus around the lower mid range. Just record some gutiar tracks and if you can encode to mp3 foramt and watch the EQ bands fly where the signal is at. I've sure there are other programs i never use that can show you this stuff real time in the program without having to go through encoding, however, moving on...yea for heavy gutiar I mess around with fading off the high frequencies and boosting the lower mid range and extreme low end frequencies at the same time sucking out the mid a bit and bosting the upper mid range to about 1 to 2 kHz. after that it's mostly harmonic overtones far as i know that are good for overall sound and filling the dead air. Also if you want you can try finding the frequency that you [pick attack sound is at and suck out that specific frequency in the mix down EQing process and get more of the actual tone to stay.

In general i say Low + Mid - High + simple as that, for clean i just record whatever, add some chorus don't worry about Eqing. Most of the sound coming out of your instrument is going to be determined by how well you can play it anyhow.

Hope that helps dude.