Abstract: Metformin has become the first-line drug for the treatment of type 2 diabetes, which is stably efficacious, safe, and cheap. Previous studies have shown that the application of metformin can decrease the rate of tumor incidence, recurrence, and metastasis. It can also improve the prognosis of cancer patients and their lifetime after long-term use. Considering its multiple advantages, metformin has become an emerging choice for the treatment and prevention of cancer. Therefore, the mechanisms through which metformin inhibits tumor metastasis in cancer therapy are worth investigating.