The angels were created by God when He created the rest of the world. Jesus describes the life of an angel in Luke 20:36:
“for they cannot die anymore, because they [Christians in heaven] are equal to angels and are sons of God, being sons of the resurrection.”
Isaiah 6:2-3 tells us that angels fly around in heaven and sing to the Lord, “Holy, Holy, Holy is the Lord of hosts. The whole earth is full of His glory!” They also give messages from God like Gabriel did for Joseph and Mary.