'Angel' in the Bible

Then the angel of Yahweh spoke to Elijah the Tishbite, "Get up, go up to meet the messengers of the king of Samaria and speak to them, 'Is it because there is no God in Israel that you [are] going to inquire of Baal-Zebub, the god of Ekron?'

Then the angel of Yahweh spoke to Elijah, "Go down with him. Do not be afraid because of him." So he got up and went down with him to the king,

It happened in that night that an angel of Yahweh went out, and he struck down one hundred and eighty-five thousand in the camp of Assyria. When they got up early in the morning, look! All of them [were] dead corpses.