Here are some clues. Hope they help!
A1: King Crimson - Lizard (Pols Voice)
A2: Ozzy - No More Tears (fadetoblackdude7)
A3: Porcupine Tree - Deadwing (Buddyhunter1)
A4: album by a noted ambient group
A5: Steve Hackett - Beyond the Shrouded Horizon (Zydar)
B1: heavy, slow, trippy
B2: Red Sparowes - At the Soundless Dawn (LieLowTheWantedMan)
B3: Ahab - Call of the Wretched Sea (lateralus88)
B4: last album before they broke up
B5: Yes - Fly From Here (Pols Voice)
C1: Symphony X - The Odyssey (Pols Voice)
C2: brutal and technical
C3: Amon Amarth - Twilight of the Thunder God (Buddyhunter1)
C4: ethereal and eclectic
C5: Ulver - Wars of the Roses (Big Hath)
D1: Eluvium - Copia (kari)
D2: staple of the ambient genre
D3: sounds like Tool
D4: mix of shoegaze and post-rock
D5: Camel - A Nod and a Wink (Mladen)
E1: mix of jazz and classical
E2: God Is An Astronaut - S/T (Jirpo)
E3: insanely technical, from a country that doesn't have any famous metal bands (relatively speaking)
E4: Pelican - What We All Come to Need (Jirpo)
E5: dark and scary at times, not metal