A few for me:
Technically, not an album, but the System of a Down songs that were played on the radio in the early 2000s. Hearing their riffs and aggression as a young kid really made an impression on me. It was what got me to begin playing the guitar, and was among the first bands that I recognized. I don't listen to them much anymore, but I have very fond memories of their music.
Metallica -s/t album: This was the first metal album that I ever got (it was a gift), and is still one of my favorites. It is a great collection of songs. All of them are catchy and memorable.
Burzum - Filosofem: This is my favorite Burzum album, and was one of the first black metal albums that I ever purchased. The ambient guitar tracks at the end remain inspiring to me, and I named my first musical project after them.
Reek of the Unzen Gas Fumes/Xenophobic Ejaculation - split: Reek of the Unzen Gas Fumes changed my view of what metal can be by pushing speed and catchy riffs to the extreme. This split has some of their best tracks. This release was also my first introduction to the mighty power electronics of XE. I had never heard music like that before, and, since hearing it, I have been converted to listening to and playing noise music/power electronics.
This is easily their best release!