My band and I are currently writing a thrashish kinda metal song that needs a fast solo. However, I am relatively lacking in experience as far as playing leads goes, and I need some ideas. I know that minor pentatonics will sound good in this environment, and so will the natural minor scale. Can you recommend any scales/modes that will sound good in this environment? Stylistically, think of Metallica/Megadeth/Pantera/Kreator. One thing that might make a difference is that, at this point, I can't sweep worth anything. Thanks in advance .
Try some harmonic minor. Just take the minor scale and raise the seventh degree a half step.
So, in harmonic minor, you play a natural minor scale, but with a major seventh instead of a minor seventh?
The simplest way is just work out the arpeggios for each chord you're soloing over and then form some kind of fast repeating patterns based on those that follow the chord tones. You'd find a lot of this kind of stuff in Megadeths solos, specifically Marty Friedman's soloing.

Or you could just play your pentatonic scales, that's all you really need, check out any metallica solo, as they're pretty much all based on Em pentatonic or the blues scale. Zakk Wylde does this a lot too.

Basically, steal ideas from the people you want to sound like, and find a way to fit it into your own song and morph what they've done into something of your own.
well, i want to kinda branch out from pentatonics some, cuz one of our other songs has a bluesy feel and i use pentatonics on it a lot. i'm looking for something darker sounding. i really like harmonic minor, so thanks to GreekRockr9 for that.