[nemothekid]

This assumption might be wrong, but it's my understanding that Metallica, GnR, and other hard rock/metal bands, while successful, are aging with their audience, which is mean by being generational. Beyonce has penetrated both 19 year olds and 45 year olds demographics with great success. I'm not sure I can say the same about Metallica.

[Yodel0914]

One of the interesting things about music since the advent of streaming is that it's far less segregated by time of release. Anecdotally, I know 18yo kids into metal who are as likely to listen to Metallica or AC/DC as they are a current-generation metal artist. I don't think there's anywhere near as much of a currency bias as there was ~30 years ago.

More anecdotes: the crowds at metal shows I've been to are quite diverse age-wise - from ~15 to ~65. The demographics don't seem to change that much with the band playing, except that that's less older people for the really heavy bands (Cattle Decapitation comes to mind).