I like Bandcamp.com because you can directly support artists you like on there. I've bought a few cassette tapes from Bandcamp releases as well. Sometimes they're too political for me. So I'd rather try to buy directly from a label if I can now. (It also saves money sometimes since Bandcamp takes a cut).
SHADOW KINGDOM RECORDS sells a lot of neat metal albums. They sell CDs, cassettes, and records and you can buy shirts and stuff from them too. The site is pretty nice as well if you ask me. It's not a bloated modern site.
Here are some ways that I download music.
First up is Soulseek, which is a program that lets you share and download files. It's really easy to use and usually I can find whatever I want on there, but not all the time.
Sometimes if you're looking for Japanese or other Asian music it's not on Soulseek. The best place for me has been the jpop80s blogspot site. It has the best selection I've seen for this type of music. Normally when I go there, I just hit ctrl+f to find text in the page and type in the artist name I'm looking for, in English. Sometimes you might have issues with how the artist's name is romanized so you might type something in, and find no result when it's there, but it's just spelled slightly differently, so be aware of that. The only downside here is that the downloads are done through a link-clicking service or whatever. I guess that's how whoever runs the site makes a bit of money, and I'm okay with it, but I end up having to enable all sorts of scripts and stuff to use it which kind of sucks. What I do is just open the download link in a private tab since I figure that's at least better than enabling a bunch of junk in my regular browser session.
Also, I think he hides the download link first behind a link shortener, and then puts THAT link behind another link shortener. So you'll have to click "get link" twice. And then the download is a .rar file, so you download that, then you extract it, and inside is ANOTHER .rar file. extract that and you'll finally have the album you downloaded. So it's a bit of a tedious process, but it only takes a couple minutes to get the download started so it's not really a big deal anyway. I definitely recommend this site.
Sometimes you can't find anything anywhere, but a lot of the time it's at least on Youtube. The audio quality won't be the best from youtube, but in my opinion, it's not really a huge deal. Not for me, anyway. The single best way to download things from youtube is a program called youtube-dlc. You may have heard of youtube-dl, it's also great, but youtube-dlc is updated a bit better nowadays, so just use that. Also it seems like there are two github links for the same program, I'm not sure what that is about. It works on Windows and Linux. In case you're a homosexual I think it works on Macs, too. It might take a bit of time for you to get used to using it properly and all the commands and stuff, but it works really well and if you learn how to use it, it can be a really useful tool. So sometimes if I can't find an album anywhere, I'll be able to download it from youtube as an audio file.