Do u think there is a metaphor in this stanza of the poem The Rime of the

[John Kelly]

Ancient Mariner? My teacher says that there is visual imagery. I agree.But i think there is a metaphor also.Bcz it is Copper Sky so sky is compared with copper metal.Isn't it a metaphor.Please help me.
All in a hot and copper sky,
The bloody Sun, at noon,
Right up above the mast did stand,
No bigger than the Moon.
My teacher says that there is visual imagery. I agree.But i think there is a metaphor also.Bcz it is Copper Sky so sky is compared with copper metal.Isn't it a metaphor.Please help me.