So the holy one to be born will be called the Son of God. Even Elizabeth your relative is going to have a child in her old age, and she who was said to be barren is in her sixth month. May it be to me as you have said. Then the angel left her. Mary was startled by what the angel said.
Nothing is said about how the angel looks.
We could infer from this that the angel's appearance was not surprising to Mary. Do not forget to entertain strangers, for by so doing some people have entertained angels without knowing it. They are more like us in that they are finite, created beings. You might want to have some fun and have the men say it and the ladies say it and those under a certain age say it and so on. When God Doesn't Make Sense is must reading for every teacher on this subject.