As a zealous Metal fan of over 30 years, I still hold true to the physical copy paradigm.
During these years I have collected a many CDs through favourite bands, and exploration into new Genre's. Hopefully through these list's you may be able to find that missing Album you have been chasing, or can discover something new.
My Lists do not contain Hard rock! Just Metal, and mixed in genres through each list. I fully advise to visit Metal Archives https://www.metal-archives.com/ to help you confirm what genre the album your interested in. It also doesn't go close to covering everything out there.
Enjoy :)