The passage in Ann and the Cow used a metaphor to compare the cow with wealth, success, and other symbolic things to enhance the reader's feelings and thoughts about the character's fate. Metaphor is a rhetorical device that makes it easier for the reader to understand and feel the meaning of the text by comparing two or more things. In Ann and the Cow, the role of this metaphor was to emphasize the misfortune and frustrations of the character's fate by comparing the cow with wealth, success and other symbolic things. It enhanced the reader's feelings and thoughts about the character's fate, allowing the reader to understand the theme of the article more deeply. At the same time, this metaphor also added some mysterious color to the character's fate, enhancing the readers 'reading ability and attractiveness of the novel.