Perhaps the SM58 is not the best mic for your particular vocals? How do the vocals sound soloed? If they are muddy, boomy, veiled, etc., maybe you could try to change the distance and/or the angle slightly that you are singing/screaming into the mic? SM58's have a serious proximity effect, where the closer you get, the more it peaks in the lower mids. A condenser mic may help that. You may need to get a preamp to run it through.

Perhaps your particular voice is occupying the same space as the meat of the guitars? If you have two guitars, especially, occupying the same frequency range, with similar tone, and then try to slip a vocal in there that lives around those frequencies, then you have at least two or three things battling it out to be heard in the same sonic space. Perhaps try to EQ out some frequencies in the guitars to leave a hole for the vocals? Especially if you have mega-distorted guitars sustaining constantly, there may be no holes for the vocals to pop through. If you have left and right guitars. you may want to give them different sounds. That may be one reason they mush together in the mixdown. If they sound too similar, they may have no identity of their own to differentiate themselves, and they may sound like there is no separation. You also have to be careful that the upper end of the bass guitar is not mushing in with the lower end of the guitar(s). For instance, if you're doing a "pissed at the world" tune with low-toned vocals, and you are eating the SM58 because there is not enough vocal energy to capture it from farther away, then you may be adding the proximity boost of the SM58, possibly in the frequency range of the main power of the guitar (or two), which also may be occupied by the upper end of the bass. Each, on its own, may sound good and powerful. Put them all together, and they may be overwhelming a particular frequency area, and no matter what you do, you can't get one to pop out without diminishing the others.

I don't know if that's the case, but it's something to explore. Try to get things out of the way of each other. That may mean EQing out either the top end of the bass, or the bottom end of the guitars. Figure out where your vocal energy is centered around, and maybe EQ out some of the other instruments in that range. It may not take much. It's probably better to cut EQ if you can, then to boost, but you may find you can cut a bit here and boost a bit there without doing much mangling of any of the affected tracks. If you are drastically cutting or boosting, perhaps start over and then do the more gentle cut/boost. For instance, if you find yourself boosting more than a few dBs, back that down, and then start cutting everything else by a more marginal degree in that frequency.

Also, using too much reverb can kill the crispness of a vocal, if it's too wet. You may try turning the wet mix down a bit.
These may not even be your problem, but just something to explore.

Hope this helped,

Kapt.Krunch

Well, vocals do NEED to "punch through" especially in Rock music. "Foggy" is definitely no good :) But, it's NOT a level issue.

The issue is probably related to EQ and Compression (and MIC pre as well).

Since your machine is Digital there is no degradation in bouncing tracks as in the days of 4/8 trk cassette 'portastudios'. However, if instruments are conflicting with each other you would end up with a sonic mush.

Get a book on the basics of EQ, Compression and mixing. It should be a good starting point.

To make the vocal punch through, it needs to be more consistent. Consistency comes with compression/limiting and some high pass filtering. The rest of the equalization is built into the SM58 and really shouldn't need much more.

Vocal compression lover
Ms. Remy Ann David