Compare one thing or situation with another. It can be divided into simile, metaphor and metonymy. It can highlight the characteristics of things and visualize abstract things. In the poem, "Looking at the Dongting Lake, the green snail on the silver plate" (Liu Yuxi's "Looking at Dongting Lake") skillfully compares the "snail" and compares the mountain under the bright moon Yin Hui to the green snail on the silver plate. The colors are elegant and the mountains and rivers are integrated.