Wow! Someone mentioned
The Green Fields of France. Good to see it represented. My own favorite lyrics would have to be Fairport Convention's version of Tam Lin, which is too long to write out here. Tam Lin is probably the best known and most documented stroy dealing with the Fae in all the British Isles and Ireland.
Link To Lyrics and Associated Resources Altogether I don't think I've heard a single version I didn't like. And there are many. Some of them are better than 50 verses long.
Every Version Known to Man