Angels are spirit beings, but when they do appear they seem to appear as humans. In Zechariah 5:12, two angels appear as women:
“Then I raised my eyes and looked, and there were two women, coming with the wind in their wings; for they had wings like the wings of a stork, and they lifted up the basket between earth and heaven.”
Throughout the rest of Scripture, angels usually appear as men. For example:
“And entering the tomb, they saw a young man clothed in a long white robe sitting on the right side; and they were alarmed. But he said to them, “Do not be alarmed. You seek Jesus of Nazareth, who was crucified. He is risen! He is not here. See the place where they laid Him. But go, tell His disciples and Peter that He is going before you into Galilee; there you will see Him, as He said to you” (Mark 16:5-7).
Some accounts in the Bible show angels with unusual feature where there is an appearance of intense light. The prophet Daniel saw an angel with arms and legs made of what appeared to be like precious stones and a burnished bronze color and a face like lightening:
“I lifted my eyes and looked, and behold, a certain man clothed in linen, whose waist was girded with gold of Uphaz! His body was like beryl, his face like the appearance of lightning, his eyes like torches of fire, his arms and feet like burnished bronze in color, and the sound of his words like the voice of a multitude” (Daniel 10:5-6).
In the book of Revelation some unusual beings are described, they could be angels of some sort:
“Before the throne there was a sea of glass, like crystal. And in the midst of the throne, and around the throne, were four living creatures full of eyes in front and in back. The first living creature was like a lion, the second living creature like a calf, the third living creature had a face like a man, and the fourth living creature was like a flying eagle. The four living creatures, each having six wings, were full of eyes around and within. And they do not rest day or night, saying:
“Holy, holy, holy,
Lord God Almighty,
Who was and is and is to come!”
As spirit beings, angels can be invisible:
“But when they urged him till he was ashamed, he said, “Send them!” Therefore they sent fifty men, and they searched for three days but did not find him.” (2 Kings 2:17).
“For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him” (Colossians 1:16).