First, let me state what a metal "classic" means to me, someone who's been around the block a few times at the ripe old age of 40. A classic is an album that I've had in my collection for at least ten years, preferably 15 or 20, and still finds it's way into my system on a somewhat regular basis. If I haven't listened to it in the past year, it probably isn't a classic in my book...unless it's a lost classic which show up every now and then and totally gets my blood pumping again like it was 1983.
With that in mind, here are a few suggestions (mostly obscure) that really made an impact on my life:
OZZY: Blizzard of Ozz, Diary of a Madman (top of the list)
Savatage: Hall of the Mountain King, Gutter Ballet, Streets
Scorpions: Lovedrive, Animal Magnetism, Blackout
Fates Warning: The Spectre Within, Awaken the Guardian
Blue Oyster Cult: Imaginos
Demon: The Unexpected Guest
Saxon: Wheels of Steel
Riot: Fire Down Under
Michael Schenker Group: Assault Attack
Fastway: Fastway, All Fired Up
Metallica: Kill 'Em All
Rainbow: Rising, Long Live Rock N Roll
Running Wild: Under Jolly Roger
Europe: Wings of Tomorrow
Kick Axe: Vices
Anvil: Metal on Metal, Forged in Steel
Alcatrazz: No Parole From Rock N Roll
Tygers of Pan Tang: Spellbound
Warlord: Best of (hate 'best ofs', but it applies here)
Coney Hatch: Best of (see above)
Malice: License to Kill
KISS: Music from the Elder
Triumph: Allied Forces
RUSH: 2112, Moving Pictures
Great White: Great White
220 Volt: Electric Messengers
Q5: Steel the Light
Talas: Sink Your Teeth Into That
Diamond Head: In the Beginning
Cirith Ungol: Frost and Fire
EGADS! That's a long list. And I'm sure I forgot just as many albums as I mentioned. Well, it's a starter list anyway. Dig deep, rock out.