Well Leeds is full of good venues and decent promoters.
A good one is Carpe Diem as it's free entry and right in the centre of town. Get in touch with a promotion group called Under the Radar or Andrei for the At The Crossroads night. Both on alternate Saturdays. No pay but always a decent size crowd and the customary free beer. Onstage sound can be a tad hit or miss but overall a nice place to deal with. And they put on all sorts.
Cockpit's a good venue and is mostly sorted through Andy at Futuresound Promotions. They generally require you to sell tickets but it's one of the better venues.
Brudenell Social Club is by far the best venue IMHO but getting a gig there can be tricky. Great place to play. they get alot of relatively 'successful' touring bands but its small and has a MASSIVE local community.
There's a bunch of other decent venues aswell but it would take an age to list them all with their promoters etc:
Milo's - city centre. Don't really put on metal but they love blues, indie, hip hop and punk
Smokestack - city centre. Funk, soul, hip hop, experimental
HiFi - city centre. Funk, soul, jazz, hip hop
These and the usual university rooms and O2 academy (unfortunately i wouldn't know;().
One last thing is a clubnight at The Library venue just outside town in Hyde Park. The night's called 360 and it's run by a chap called Richard Watson. He's the best promoter in Leeds and does loads for 'unsigned' local bands but he may well help out of town bands/artists too. He puts on loads of different styles but they generally sit well together.