Hm, apparently not as easy as I thought. Hints below.
Defender of the Faith wrote:
1. Fool just another fool just another
2. There is a place far from her home, she strayed her path too long
3. I met the old man in the depths of the woods
4. Don't walk the cold and ruthless streets
5. Now the first day that I met ya I was looking in the sky
6. I got *song title* by you and, closer than most to you and
7. I've marched to wars, with a vicious rage
8. *song title* syttyneet kaukana sieltä missä lehväin suoja yllein kumartuu
9. In the dark of my cage I can remember my freedom
10. The long northern winter has come, we march through the snow that reminds us our home
11. Somebody, somebody, come to my side
12. Cleanse my wounds in winter moon desire, this endless quest for sanctuary pure
13. Now that you've made your choice - *song title*
14. She is waiting to kiss my hand, but she will wait for my command
16. Down from the Heavens, up from the sea, they came looking, looking for me
17. The seventh had seven descendants
18. Powers of Thagerion, watch the great beast to be
19. We are the pirates of Vilayet Sea, sailing away to lands of mystery
20. As I'm looking at the throne, shadowing misery, reality unveils
1. One of the biggest power metal bands around, from Germany. Not much to say about the song.
2. Also one of the biggest power metal bands around, from USA. The song is from their most well known album (probably) but it sounds a bit different from the rest of the album.
3. A symphonic-folk-progressive-speed metal, or maybe just power metal, band. Strangely not that popular. From the smallest nation in Scandinavia.
4. A Canadian power/heavy metal band. Probably their most well known song. People either really like them or really don't.
5. In my opinion, the very first metal band, from their very first album.
6. This might very well be THE most popular band in the world right now, especially after they released their latest (double) album. This song is a couple of years old though.
7. A Greek power metal band. Not that famous, as far as I know.
8. Finnish viking/pagan metal band. One of their best songs, from their second album.
9. Italian symphonic power metal band, quite similar to another, more well known, italian symphonic power metal band. They sing about this french witch chick, who the entire album is about...
10. Italian epic metal band. The album is about vikings killing people in england.
11. A british hard rock band, very famous, from their most famous album.
12. British epic doom metal band, one of the biggest, though still not THAT well known. From their first album.
13. Outro on one of the most important power metal albums, from Germany.
14. Bonus track on an album made by one of the biggest power metal bands, from USA. The song is... special.
16. American cult epic metal band, from their latest album.
17. Opening track on a very special concept album. Was released a couple of years ago and it's very good. If I say which country the band is from it'll be too easy.
18. Swedish symphonic metal band, very famous. From one of the most important symphonic metal albums.
19. Epic metal band from Portugal, people say they sound a lot like Manilla Road.
20. Canadian progressive death metal band from their debut album. Very good album. If you're on the TMO forums you most likely know about them.
That should make it a lot easier. Keep in mind they're all different bands.