When employing "figurative language," writers use words and language in ways that are different from the literal meanings of the words. Metaphor and simile are two examples of figurative language. In "Gratitude to Old Teachers," Robert Bly writes about a frozen lake, which "we stride or stroll across." This poem uses figurative language, because the poet is not simply literally describing walking across a frozen lake. Rather, the frozen lake represents something else about a student's journey and the teachers that he or she learns from. In this poem, the frozen lake is a metaphor, since it represents something greater or other than a literal frozen lake.
In particular, the last line in the poem is an example of language being used figuratively:
Beneath us the teachers, and around us the stillness.
This is an example of figurative language because the teachers are not literally underneath the lake or standing beneath the students. Rather, the poet describes the teachers as "beneath us" to create a metaphor for the ways in which the students are influenced by and inspired by their former teachers.
Examples of rhythm in the poem can be found in the way the lines are broken up and the amount of syllables per line. You might try reading the poem out loud to get a sense of the rhythm of it. It might also be said that the rhythm of the poem could represent the pace of people walking across a frozen lake, one step at a time.