Angels appear, announcing the birth of a Savior in the city of David — David, who is also a shepherd, one of some note.
The angels come to humble men in the midst of their occupation. (Jesus does this often. He finds Peter the fisherman in the midst of fishing, Matthew the tax collector in the midst of collecting taxes. He interrupts lives, saying ‘Come, follow Me.’)
The angels interrupt the shepherds, announcing that a Savior is born to them. The Savior is come to save them.
This is Jesus’ message. He tells us He has come to save us from ourselves, from our sins, from our separation from God, from death itself. This is the good news.