Tip lang (I've forgotten where I got this article....)
Back off the Gain!
A heavy sounding band is the result of the whole bands efforts, not just one guitarist. It is a common practice for heavy music to double or even layer multiple guitar tracks to get a heavy tone. If all of these guitar tracks were super high gain you'd get mush.
Of course there is exceptions to this; industrial and death metal and such often use super saturated high gain sounds (although one of the guitarists for Opeth was quoted as saying the trick to creating a wall of guitar was to use very little gain on rhthym parts). But for most hard rock and metal, there is way less gain going on with the guitar than you may think. It is the coupling of a distorted (not super saturated) guitar with the bass, drums, vocals, and other guitars that leads to a heavy sound.
A good example I can think of is Metallica, particularly Load and Reload. I choose these albums because they did less layering than on previous works. Most of the time on both of these albums it is simply James playing on the left (I believe) and Kirk on the right, just two guitars. Metallica, regardless of whether one likes them or not, is generally percieved as having a really heavy saturated metal sound. Put on some headphones and try to single out one guitar in those moments when only one guitar is playing, and I bet you can catch that those guitars, on thier own, are not nearly as distorted as you may have once thought. They are distorted and heavy, yes, but the gain is not cranked to the point of fuzz. They get as much gain as they need to get a nice twangy chunky sound and that's it. You can't really have twang and fuzz at the same time. Then these guitars are combined with each other, with nice heavy bass and powerful drums and the result is a clear, heavy, ballsy sound. If they put more gain on those guitars you'd lose clarity and balls, becuase the more gain you add the closer you get to a Fuzz Box sound.
This is something many inexperienced players don't know yet. (Not that I'm a guitar god or anything ) They have the sound of a huge sounding band in thier minds and they try to duplicate that sound with just a guitar, but the guitar is only one element, one of many, and the gain of the guitar is not as essential to a heavy sound as it may seem.
When I first got a POD 2.0 I thought it sounded like crap because all of the presets were so fuzzy. Then I backed off the gain, much better. I stepped up to the PODxt and again the stock presets were way too heavy in the gain department, but again backing off the gain cleared things up nicely and eliminated much of the fizz. Fizz is just a consequence of tube breakup, it's not some huge inherent problem in the PODxt. The thing is that the amps in question, and consequently the models based on them, are capable of more gain than is useful most of the time. For instance, on my main Soldano patch the gain is never above half way, and a lot of the time it's at about a third with a bit of Vetta Comp to keep the sustained breakup a bit better, and it's as much gain as I need for seven string heavy riffage. I'll never even use half of the gain the SLO (and it's model) is capable of, and I play some pretty heavy seven string stuff.
Back off the gain more than you might think to and slam around on it awhile. You might be surprised how heavy and cool it sounds, and it might even sound a lot more like the record than you'd think.