Folk Metal has been around sense the 1990's. The earliest band that created this genre of music had to be Skyclad. They had an offshoot of heavy metal that included folkish instruments and folk singing. In Europe there is a lot of tradition, tales, stories and history that goes along with folk metal. This region is where most folk bands get their ideas and metal music inspiration from. Romanticism and pagan beliefs are some of the more popular structures of folk metal music.
Oriental metal, Viking metal and Celtic metal are some other subgenres in folk metal. The band Cruachan arguably started the Celtic metal genre when the guitarist expressed interest in fusing traditional black metal with the folk music of Ireland. Primordial and Waylander help make the transition to folk metal.
In the early 1990's the band Orphaned Land started an unusual and sometimes weird melding of Arabic and Jewish death metal progressive undertone style of music. This started of a new subgenre of music, Oriental Metal.
This was the start of the genre Viking metal. Viking metal will give you a healthy dose of Nordic paganism and mythology that are combined with powerful ballads. Viking themed lyrics have been enjoyed in all mainstreams and popularity of metal music. Amon Amarth has produced some of these Viking lyrics and placed them in death metal. A Swedish Viking metal band called Ensiferium has put them on top of the list for Viking metal.
Masculinity and Nationalism are prideful in Folk metal. These are usually not very popular or accepted by the metal community. Most bands will have publicly denounced racism within their music because of this.
Folk metal has really inspired a bunch of die-hard fans with many festivals dedicated to the genre. Heathen Fest, Noctis Valkyries and Notably Paganfest Metal Festival. As time goes on and the genre expands these tours and festivals have made their way from the cold northern lands from whence they came across the sea to the States.
Folk for the future has been known to be a 'passing fad', but not likely. There is esoteric nature of the music and the realms of endless possibilities. For the metal community, folk metal will always have its place for those fans that want a different and unique style of metal music.