Welcome To Ireland Jules, I hope you're having a good time
The Limelight Belfast is regular for Rock/Metal.
There's the Monsters Of Rot in Co. Fermanagh. http://monstersofrot.com
The Voodoo Lounge and On The Rox in Dublin are 2 main venues for gigs.
The Academy is another place in Dublin too that can have Rock/Metal gigs too.
Rosin Dubh in Galway has live gigs too.
Fred Zepplins in Cork is a big one in Cork.
There were more festivals but they stopped for various reasons.
They're a few, and I hope they help, a few leads there.
All the best Jules.