Amp sims?

Like probably anybody who would see this, I do some (very low-level) home recording stuff. I just moved half-way across the country and decided that it was a great opportunity to turn my amp into money, so I did. I'm maybe coming up on working on something to record again now, and I read about amp sims being maybe just as good as live amps, but I don't know a thing about them. Is there any good place to start? I would love free, but can spend some if I need to. Anything I need to know? I'm not super tech-savvy nor super music-production savvy, but can usually muddle through when I have enough motivation. 

Thank you to anybody who takes the time to reply!

edit: would be for death metal type stuff if that makes a difference