I am not sure about U2, but Metallica do decent to their fans through available content, access to older live shows, etc. Also, Metallica does not release albums often so their fans and casuals see the release of an album as an event. Importantly, their albums are still mostly liked. Hardwired, thier last album from 2016 sold over a million copies in the U.S. alone during 2017 and around 300,000 album equivelent units in its first week. It is somewhere over 2 million units now.

It was propelled by packaging the album with ticket sales, but I think
Metallica's audience is still there, I don't think Bon Jovi's is. Although, I think Jon will continue to make music over the next decade regardless.