What do angel ornaments on Christmas trees symbolize?

It is one of the Christmas tree traditions. Angel ornaments are placed at the top of Christmas trees to signify the prominent role played by Angels in the birth of Jesus Christ. An angel appeared to Mary to tell her she will conceive of a son named Jesus, an angel appeared to Joseph to tell him he will be Jesus' earthly father, an angel appeared in the sky over Bethlehem to announce and celebrate Jesus's birth.