Adam Clarke on Matthew 28:3

His countenance - His appearance, ἡ ιδεα αυτου; or, his face, for so the word is used in some of the best Greek writers. It seems, from Mar 16:5, that this angel had assumed the appearance of a young man.

Like lightning - Coruscations of glory continually flaming from his face. This might produce the confusion mentioned Mat 28:2.

His raiment white as snow - He was clothed in garments emblematical of the glad tidings which he came to announce. It would have been inconsistent with the message he brought, had the angel appeared in black robes, such as those preposterously wear who call themselves his successors in the ministry of a once suffering, but now risen and highly exalted, Savior. But the world is as full of nonsense as of sin; and who can correct and bring it to reason and piety?