Hark! The Herald Angels Sing is a theologically rich song. It’s perfect for Christmas Eve, the night in which the angels visited the shepherds.
Luke records the event:
13 And suddenly there was with the angel a multitude of the heavenly host praising God and saying,
14 “Glory to God in the highest, and on earth peace among those with whom he is pleased!” – Luke 2:13-14
Merry Christmas! and enjoy the song.