This is where a good quality hardware channel strip is worth it's weight in gold.
For Metal, we use a fast FET style comp/limiter to catch the peaks on the way in and give the vocal that aggressive character. ( Distressor, UA 6176, anything in that catagory...Presonus Eureka is the cheapest alternative to those spendy ones that dos'nt suck and you can sweep the transformer )
If the vocalist is too far from the mic, ( over 12 inches ) you will get more of the room and less of the mouth and vocal bite. This is where a pop filter is most important especially with brutal/death screams and growls.
The mic is key here for metal as well..Shure SM7b is the goto mic for most metal/hard rock. Its not the most expensive but, Its the standard. If you cant pop for the 300 bucks then beleive it or not, a 58 with a pop filter will come pretty close but you will have to crank the crap out of both of them as they are dynamic and not condensor mics....this is where the mic pre-amp / channel strip starts to earn it's money.
Its garbage in, garbage out...one good channel strip will make the most of an inferior audio interface's mic pre's and save you work later. The goal is not to overcompress on the way in, its to keep from clipping while capturing all the crazy dynamics that a metal vocalist is gonna throw at you.....from wild screams to whispers.
Sonar has a great compliment of comps once your tracked and you can tweak till your hearts content after the fact.