You will probably feel “out of place” and there will probably be few people of your demographic… But no one cares. If you enjoy your time with your wife and enjoy the concert, it doesn’t really matter.

I been to a bunch of goth metal concerts as a middle aged man. It’s mostly young people dressed in black goth apparel. I’m there as a serious middle aged guy in a normal T-shirt and jeans. It’s never been a problem. Many times the other concert goers will be quite welcoming to share their music taste with someone.