Ai Qing compares an umbrella to a selfless person in his poem. Whether it is rainy or sunny, it helps people. On rainy days, umbrellas keep people from getting wet; On a sunny day, umbrellas become clouds over people's heads again. This spirit of selfless dedication is what people in society need to learn and pursue.
Ai Qing used rhetorical devices such as personification and parallelism in his poems, and personified the umbrella through the self-description of things, so that it could tell his own experiences and thoughts. This way of writing makes poetry more vivid and interesting, and at the same time better expresses the theme of umbrella's selfless dedication.
Ai Qing sublimated the theme at the end of the poem, and he praised the dedication through the expression of umbrella.