Here's a very random selection (youtube links):
Aq Bure - Tan Aldy / Ак Буре - Тан Алды (Tatar folk metal)
Auļi - Sūda dziesma (Latvian folk music, with medieval bagpipes)
Wolfmare - Twa Corbies (A Russian band's souped-up rendition of Steeleye Span's rendition of an old English folk song)
Flickan går på golvet (Swedish, with "keyed fiddles")
Erja Lyytinen - Not a good girl (American blues, from Finland)
Moonsorrow - Raunioilla [At the Ruins] (One of the most important Finnish folk metal bands, but probably unknown to most Americans. I included this partly for the incredible photography of Scottish ruins and landscapes.)
My big thing is Polish bands, especially those that came up in the 80s, while still behind the Iron Curtain.
Republika - Biala Flaga (White Flag)
https://www.youtube.com/watch?v=6sDqEhud8c0
Kult - Hej Czy Nie Wiecie (Hey, Do You Not Know?)
https://www.youtube.com/watch?v=yia6Y_ST7IY
Lady Pank - Zamki Na Piasku (Castles in the Sand)
https://www.youtube.com/watch?v=lGZ1mdkF3Bo