Deck the hall is a joyful song that has always been used at Christmas parties.
The melody comes from Wales and is a reworking of the song Nos Galan (whose translated title means New Year’s Eve celebration or gift).
In the first publication of the song (Welsh Melodies vol. 2 from 1862), there are two texts, one in Welsh and one in English. The English text is titled Deck the Hall and becomes one of the most popular Christmas songs.
Here is the sheet music of the melody (which repeats over the three verses), the mp3 files for listening and the backing track, and finally the lyrics with the translation.

Deck the hall with boughs of holly, Fa la la la…
‘Tis the season to be jolly, Fa la la la…
Fill the mead-up, drain the barrel, Fa la la la…
Troll the ancient Christmas carol, Fa la la la…
See the flowing bowl before us, Fa la la la…
Strike the harp and join the chorus. Fa la la la…
Follow me in merry measure, Fa la la la…
While I sing of beauty treasure, Fa la la la…
Fast away the old year passes, Fa la la la…
Hail the new, ye lads and lasses, Fa la la la…
Laughing, quaffing, all together Fa la la la…
Heedless of the wind and weather, Fa la la la…
The melody repeats the same way in the three verses, while there are some differences in the accompaniment. In fact, in the first performance I emphasized the C drone, thinking of a piece for bagpipes. In the second performance, you start to hear the second voice (shown in the sheet music with small grey notes), which is played in full in the third part.