in this poem emily dickinson has created a metaphor poem. she is comparing two things. please explain the two things that she is comparing. use examples from the text to explain your meaning

The basic metaphor for this poem is the comparison of a train to a horse. "I like to see it lap the miles and lick the valleys up." The interesting thing in this poem is that the word train and the word horse are never mentioned so the reader has to read the poem thoroughly and see what the words she uses actually refer to; this is a metaphor in which both the literal and the figurative are not mentioned.