You could do worse than check out Cordelia's Dad's first album. The name of the album escapes me, but it's got the Baby Song, Banks of the Lee and a few like that on. After the first album they ditched the metaly stuff and became more melodic, with interesting results.

There was also a band knocking about called 'We Saw The Wolf' that I vaguely remember seeing. I know nothing else about them other than the fact that they claimed to be a 'folk metal' band and they entertained a 16-year-old me 20 years or so ago.

Finally, You Slosh would possibly be worth a look. Mainly pipe stuff, but with what I'd consider a 'heavy metal' approach. Their gigs were scarier than any of the heavy metal gigs I ever attended. Their first album, with 'The Break' on, still gets the odd airing in my house.