Angels take any form they wish in the physical world.
Angels can come as birds, as human beings, or as a form of light like a rainbow adorning.
They do not retain their full original form of light when they are sent to human beings: "Say: If there were in the earth Angels walking secure, We had sent down for them from heaven an angelwithout change] as messenger" (17:95).
As crystal water takes the form of the cup in which it is poured, Angels can take the form of any creation which they visit.
Angels take any form they wish in the physical world