'Angel of the Lord' in the Bible

But the angel of the Lord said to Elijah the Tishbite, Go now, and, meeting the men sent by the king of Samaria, say to them, Is it because there is no God in Israel, that you are going to get directions from Baal-zebub, the god of Ekron?

Then the angel of the Lord said to Elijah, Go down with him; have no fear of him. So he got up and went down with him to the king.

And that night the angel of the Lord went out and put to death in the army of the Assyrians a hundred and eighty-five thousand men; and when the people got up early in the morning, there was nothing to be seen but dead bodies.