The precise identity of the “angel of the Lord” is not given in the Bible.  However, there are many important “clues” to his identity. There are Old and New  Testament references to “angels of the Lord,” “an angel of the Lord,” and  “the angel of the Lord.” It seems when the definite article “the” is  used, it is specifying a unique being, separate from the other angels. The angel  of the Lord speaks as God, identifies Himself with God, and exercises the  responsibilities of God (Genesis  16:7-12; 21:17-18; 22:11-18; Exodus 3:2Judges 2:1-4; 5:23; 6:11-2413:3-222 Samuel  24:16; Zechariah  1:12; 3:1; 12:8). In several of  these appearances, those who saw the angel of the Lord feared for their lives  because they had “seen the Lord.” Therefore, it is clear that in at least some  instances, the angel of the Lord is a theophany, an appearance of God in  physical form.

The appearances of the angel of the Lord cease after the  incarnation of Christ. Angels are mentioned numerous times in the New Testament,  but “the angel of the Lord” is never mentioned in the New Testament after  the birth of Christ. It is possible that appearances of the angel of the Lord  were manifestations of Jesus before His incarnation. Jesus declared Himself to  be existent “before Abraham” (John 8:58), so  it is logical that He would be active and manifest in the world. Whatever the  case, whether the angel of the Lord was a pre-incarnate appearance of Christ  (Christophany) or an appearance of God the Father (theophany), it is highly  likely that the phrase “the angel of the Lord” usually identifies a physical  appearance of God.