When Jesus was born, God wanted to announce the news to his people. So he sent a host of angels to communicate the message to some shepherds. Sending this announcement to shepherds, of all people, might seem like an odd thing to do. Why not have the angels appear to the king or to the leading Jewish or Roman authorities? Why not the high priest or the Sanhedrin? Of course, God has a plan in mind. Jesus came for a very particular purpose—to die as a sacrifice for the sins of his people. Had this announcement been made to the king or to the leaders of the Jews, the outcome of Jesus’ life would have been different.
The purpose of the angels was to communicate the fact that Jesus had been born. They came with a message announcing this important event. And the focus in this passage is the message. The shepherds experienced something phenomenal, even miraculous; but what was most important was the communication, the message communicated from God, through the angels, to the shepherds, and from them to others.
I think we see a pattern here. God communicates a message to his people; they respond to that message in faith and obedience; then they go out and communicate that message to others. We still follow that pattern today. God communicates to us through his word, we believe it, we act on it, and we tell others.