Angels, Can appear in various forms

As an adult man.

Genesis 18:1-2 (ESV)

^1  And the LORD appeared to him by the oaks of Mamre, as he sat at the door of his tent in the heat of the day.

^2  He lifted up his eyes and looked, and behold, three men were standing in front of him. When he saw them, he ran from the tent door to meet them and bowed himself to the earth

As a young man.

Mark 16:1-7 (ESV)

^1  When the Sabbath was past, Mary Magdalene, Mary the mother of James, and Salome bought spices, so that they might go and anoint him.

^2  And very early on the first day of the week, when the sun had risen, they went to the tomb.

^3  And they were saying to one another, “Who will roll away the stone for us from the entrance of the tomb?”

^4  And looking up, they saw that the stone had been rolled back—it was very large.

^5  And entering the tomb, they saw a young man sitting on the right side, dressed in a white robe, and they were alarmed.

^6  And he said to them, “Do not be alarmed. You seek Jesus of Nazareth, who was crucified. He has risen; he is not here. See the place where they laid him.

^7  But go, tell his disciples and Peter that he is going before you to Galilee. There you will see him, just as he told you.”

As a shining, non-earthly being.

Daniel 10:4-6 (ESV)

^4  On the twenty-fourth day of the first month, as I was standing on the bank of the great river (that is, the Tigris)

^5  I lifted up my eyes and looked, and behold, a man clothed in linen, with a belt of fine gold from Uphaz around his waist.

^6  His body was like beryl, his face like the appearance of lightning, his eyes like flaming torches, his arms and legs like the gleam of burnished bronze, and the sound of his words like the sound of a multitude.

Large, fantastic humanoid shape with other-earthly characteristics.

Revelation 10:1-3 (ESV)

^1  Then I saw another mighty angel coming down from heaven, wrapped in a cloud, with a rainbow over his head, and his face was like the sun, and his legs like pillars of fire.

^2  He had a little scroll open in his hand. And he set his right foot on the sea, and his left foot on the land,

^3  and called out with a loud voice, like a lion roaring. When he called out, the seven thunders sounded.