I’m looking to buy more CDs and expand my depth and breadth of metal music appreciation. Instead of “greatest hits” I’d like a studio (or live) album that is a shining example of a great band.

I’ll start:
Ratt: Out of the Cellar
Listen

This was Ratt’s breakthrough hit and debut album that put them on the map. Several hits on this disc like “Round and Round”. Also a couple great songs that were not hits like “Lack of Communication” and “I’m Insane”.

Edit To Add: Some great responses below, thanks! Please feel free to ponder further and add to your response or respond again with other bands!