Angels were messengers who appeared in the form of a man to different people.
The Old Testament frequently refers to the Angel of the LORD. This was a special messenger of God. The traditional interpretation is that this was an appearance of Jesus Christ, the Word of God, in human form, also called a pre-incarnation of Jesus the Messiah.
Only in the last centuries Bible interpreters have suggested that the Angel refers to different angels, rather than Jesus. However, Hagar called out, “You are a God of seeing,” (Genesis 16:13) and God told Moses and the Israelites, “Pay careful attention to him and obey his voice; do not rebel against him, for he will not pardon your transgression, for my name is in him” (Exodus 23:21).
Only Jesus was able to forgive sins (Luke 5:20) and only He bore the name “I am” (John 8:58). Thus the Angel of the LORD distinguishes himself from the other angels, who are servants (Hebrews 1:7).
For further study, go to Angel of the LORD