15 tracks tops unless it's a band doing 30-second songs.

Don't think Metallica hasn been done before, probably because you could only fit 8 of their best on a CD, but...

Blackened
For Whom the Bell Tolls
Battery
Master Of Puppets
One
Leper Messiah
Welcome Home (Sanitarium)
Sad But True
Fuel
Nothing Else Matters
Hero of the Day
The Shortest Straw
Creeping Death
Seek And Destroy

Sub-question: Would this tracklist be your ideal live set for the band to play?