Raven was an integral part of the New Wave Of British Heavy Metal and one of the main influences behind "Speed" and "Thrash" Metal.  

The trio were sometimes closer to punk than Metal, especially their live shows that usually left their fans in a frenzy as well as a pile of smashed equipment.  As their career evolved they became a more traditional Power Metal band, even though bassist/vocalist John Gallagher's vocals were always more spastic than say a Rob Halford.  His brother and guitarist Mark was actually a very accomplished virtuoso guitarist which made the music more "Metal" than "Punk".

Here's a couple videos from early in their career during a live performance on the BBC.