Glam? Calling trixxi and conney
As for traditional heavy metal (fasten your sealt belts):
Judas Priest: up to "Painkiller"
Iron Maiden: up to "Seventh Son Of A Seventh Son"
Demon: up to "The Plague"
Tank: debut at least
Motorhead: all!
Tokyo Blade: fist two albums (with Alan Moore on vocals)
Diamond Head: debut
Black Sabbath: just skip "Forbidden"
Abbatoir
Angel Witch: debut
Armored Saint: debut and "Symbol Of Salvation" especially (but all are good)
Avenger
Axe: especially "Nemesis" and "Offerings"
Black Knight: good luck finding it but it worth every dime
Blitzkrieg: debut and/or anthology
Hawk
H-Bomb
Sortilege
Gargoyle
Jaguar
Praying Mantis: debut and "Nowhere To Hide" especially
Riot: most are great, I'm not sure about Rhet Forrster era.
Saxon: all!
Skid Row: with Sebastian Bach
Tobruk
Thin Lizzy: for the more metal edge from "Chinatown" on, but all should be mandatory!
Warlock
Witchfinder General
Manilla Road: "Crystal Logic"
Warlord
Warhead (UK)
Baron Rojo: first five albums
Hermetica
Rata Blanca
Logos
Def Leppard: first three albums (only!)
Exciter
High Power
Killers (FR)
on the thrash zone:
Anthrax: with Belladona but skip the rap shit
Metallica: first four albums
Megadeth: up to "Crypting Writngs" with some doubts
Meliah Rage: all
Metal Church: Howe's era is best, the new is weak IMO
Testament: skip "Demonic" and "The Ritual"
Coroner: all!
Heathen: debut
Flotsam And Jetsam: first two at least
Death Angel: debut and "The Art Of Dying" especially
Imperium
Kreator: "Endorama" and "Outcast" for me
Horcas
On a modern note:
Angel Dust: first two are oop and more thrash, the second era kick ass!
Wolf
Dream Evil
Blind Guardian
Helloween
Heavens Gate
Hammerfall
Angra
Freedom Call
Amorphis: especially from "Tuonela" and up (or "Elegy" depending on who you ask)
Avalanch: first three albums
Astral Doors
Azrael (ES)
Cryonic Temple
Demons & Wizards
Goddess Of Desire
Manigance
Malediction
Majesty
Mesmerize
Steel Prophet
Stormhammer
The slow note:
Solitude Aeturnus
Candlemass: with Messiah Marcolin
Solstice
Cathedral: maybe skip "Supernatural Birth Machine"
Well Of Souls
Last Chapter: debut
Thunderstorm
Krux
Abstrakt Algebra
Damn at this rate I'm going to quote almost my whole collection! Start from here