What is the function of double rhetoric in poetry?

Duality is to express two opposite or similar meanings with a pair of sentences or phrases with the same structure, equal words and opposite words. Its main functions are neat symmetry, strong sense of rhythm, high generality and beautiful music. For example, "Leaves fall like the spray of a waterfall, while I watch the long river always roll forward" (Du Fu's Ascending the Mountain), from the perspective of composition structure, this poem consists of four sentences and eight sentences, each of which is antithetical and natural. We can't see the chisel marks. "Boundless falling wood" makes the artistic conception of the poem broad and far-reaching, and the sound of "rustling leaves" makes people feel more colorful about the rolling water. More importantly, we feel the pain of the poet's fleeting youth and hard-won ambition. There is also metonymy, that is, borrowing related things instead of expressing things. Can make the language concise and implicit. For example, in To the Air, the poet praised friendship, family, people's beliefs and ideals with the concrete thing of air. There is also exaggeration, which is a description of the image and characteristics of things, and plays a more prominent and vivid role in expressing things. For example, in the long-wall ballad, "You have Wan Li's body in the fire when you mention it". This expresses the poet's own blood boiling. Then rhetorical questions are used to strengthen the tone, stimulate readers' feelings and leave a deep impression. Puns are used to add content, make expressions more subtle and euphemistic, and sometimes they are humorous. Mastering the above methods will help us understand the theme of poetry and appreciate the truth, goodness and beauty expressed in poetry, because rhetoric plays a lubricating role in expressing the author's feelings. Of course, the analysis of rhetorical expression effect should not be limited to the above theory, but also go back to specific poems and appreciate them in detail in combination with specific poems and artistic conception, so as to apply them.