There are three important bands: Mortiis, Finntroll[?], and Arckanum[?]. Whilst serving as a good genre for these bands to expand their musical style, they usually try to stay close to their usual lyrics. It is for the aforementioned reason that the three major bands sound so different: Mortiis, with a Medieval Ambient sound (no longer as current); Arckanum, with a pretty simple Black Metal sound, only with Trollish lyrics; and Finntroll with a Black Metal/Polka mix.
Here are some Troll Metal Bands:
wikipedia.org dumped 2003-03-17 with terodump