If you haven't ever heard anything from Sodom, then you might want to know a little bit about their sound. They went through quite some changes over the years starting with early Black Metal on their first two releases which sound like a mixture of Venom, early Bathory and Destruction. Are you familiar with any of the German 80s Thrash bands at all (e.g. Kreator or Destruction)? I'd not recommend these to start with though. I like 'em a lot, but I guess, you have to be really into Sodom to find them at least interesting.
Anyway, things were progressing after that and their style changed to pure Thrash. That's the way I like them best and most fans agree with me on this. So I believe, that if there is anything at all which you might like from this band then it'll be Agent Orange ('89) and Persecution Mania ('87). You can't go wrong with these two.
On the next effort, called Better Off Dead, Sodom tried to introduce a few Motorhead- and AC/DC-elements to their sound. A decent album, although many disagree with me. 1992's Tapping The Vein saw them return to pure Old School Thrash and a year later they re-surfaced with a Punk-ish approach on Get What You Deserve. I was totally into it when it hit the racks at first but meanwhile I think it stinks. You know, it's like you listen to it for the first time and go: wow, these guys sure have some powerful tracks there. But after a while the songs become more and more boring.
Next release was Masquerade In Blood and although Sodom returned to their Thrash roots once again, I really have a hard time listening to it. That's just my opinion, but I can't think of a single song on it which I like.
Things got better again with 'til Death Do Us Unite but still it is just an average output. It took Sodom another two years to come back with a real skullcracker. Code Red is as fast and heavy as Thrash can get. When I first heard the opening track I mistook it for the new Slayer record. This is also a good album to start with.
The last release so far is M-16 which left pure Thrash and offered some catchy chorus tunes. It's not as fast nor as heavy as it's predecessor but if you don't have any problems with mid-tempo albums this one also might be of interest.