The poem itself can be metaphor. In Premonitions: the Kaya anthology of new Asian North American poetry Patricia Ikeda’s “Wild Iris” has the poem growing rather like a plant. The poem grows its own way, defying some of the poet’s preferences, “I wanted to describe the wild iris / … / But instead this poem wants to express …”
The poet muses about the state of the world & family life, what she “knows” about this or that, then comes back to her perplexity at the poem, “I cannot guess / what this poem wants to be, growing / … into my life. … This poem says / it doesn’t want to end … / … it wants to rise up / amid the ordinary course of our lives.”
Perhaps the poem as metaphor is a genre. I know I’ve written many variations.