Acts 10:3-4 NLT
3 One afternoon about three o’clock, he had a vision in which he saw an angel of God coming toward him. “Cornelius!” the angel said.
4 Cornelius stared at him in terror. “What is it, sir?” he asked the angel.
And the angel replied, “Your prayers and gifts to the poor have been received by God as an offering!
Cornelius was a Roman official who had been kind to the Jewish people. God recognized his faithfulness and rewarded him. He sent Peter to Cornelius to bring the complete Word to the Gentile Cornelius.
Daniel in the Old Testament had a similar response to an Angel: terror!
Other instances have them (Angels) appearing as men without much distinction.
Angel means: “messenger.”