Well I've been checking for places with other metalheads and I dunno, UK facebook groups are quite dead for that it seems. Unless there's a secret Illuminati metal clubhouse I don't know about.
As for Twitter?
pls no I hate twitter. Don't make me go back there D:
Is metal on the decline? I don't think it would be considering like Wacken gets sold out instantly.
Back in the old days to advertise sites like this one we would band together as a community and put big signs up at gigs and hand out flyers at various metalhead bars/pubs and it actually worked cause the sites got huge member increases from it.
Although that said, people would literally just come on these kinda sites to meet people near them so they didn't have to go to gigs alone and I guess other social media like meetup.com has that covered now. *shrug*