In summary, this study not only revealed that, among m6A modulators, only METTL3 played an important role in TNBC metastasis, but also demonstrated that the low expression of METTL3-reduced m6A modification could promote TNBC metastasis by up-regulating its target gene, COL3A1. Our results provided sufficient evidence of the important epigenetic role in the development of TNBC and allowed a more comprehensive understanding of the mechanism of tumor metastasis. The gene discussed is COL3A1; the disease is neoplasm.