The Guide to Literary Terms defines "metaphor" as
a figure of speech in which a word or phrase is applied to a person, idea, or object to which it is not literally applicable. It is an implied analogy or unstated comparison which imaginatively identifies one thing with another. This device is used by an author to turn or twist the meaning of a word.
Briefly, a metaphor is a direct comparison of two things without "like" or "as." For instance, "my love is a rose" is an example of metaphor. I'll identify one metaphor in the poem to get you started on finding others.
The author uses a metaphor in the following lines:
you see it too
and you realize how that image
is simply the extension of another image,
that your own life
is a chain of words
that one day will snap.
Now, reread the poem and see if you can find any other examples.