Answer:
Debatable. I could argue this in about three directions. To be safe, call them rock. To be more specific, heavy rock. Some people would probably argue glam metal (and if you look at early photos, it's easy to see why). However, Guns are a mash-up of genres, influence-wise; Slash and Axl certainly liked quite a bit of classic rock, although they both had very diverse tastes. Duff was a bit punk, and you can hear that in a lot of Guns' music.