Try doing it in stages;
Stage 1: Early Hard Rock
Jimi Hendrix - Are you Experienced?
Rolling Stones - Let it Bleed
The Who - Meaty Beaty Big & Bouncy
Stage 2: Classic Rock
Ziggy Stardust and the Spiders From Mars
Led Zep IV
Black Sabbath - Sabotage
Stage 3: Punk
Clash - S/T
X - Los Angeles
Ramones - Rocket to Russia
Stage 4: Alternative Rock/Grunge
Janes Addiction - Ritual de lo Habitual
Red Hot Chili Peppers - Blood Sugar Sex Magic
Soundgarden - Badmotorfinger
If the person likes the last group, particularly Soundgarden, they're cleared to proceed to the next group.
Stage 5: Heavy Metal
Judas Priest - Screaming with a Vengeance
Iron Maiden - Power Slave
Motorhead - Ace of Spades
Stage 6: Thrash
Slayer - Reign in Blood
Metallica - Kill'em All
Megadeth - Rust in Peace
They're metalheads if they make it all the way to 6, and there are many more types of sub-genres to explore.
