Abstract: N6-methyladenosine (m6A) is the most common epigenetic modification in RNA. Methyltransferase like 3 (METTL3) is an important enzyme that is involved in m6A-regulated RNA metabolism, in other words, splicing, transport, translation, and degradation. Recent studies have confirmed that METTL3 plays a critical role in human cancer and influences cancer progression. METTL3 regulates cancer development through multiple mechanisms, in other words, methylation, transformation of cancer cells, mRNA stability, relevant signaling pathways, and apoptosis. Therefore, understanding cancer development and clarifying the mechanisms by which METTL3 regulates cancer progression have theoretical significance and diagnostic and therapeutic implications. This article analyzes and discusses the mechanisms by which METTL3 controls the development of various human cancers and summarizes the progress on understanding the role of METTL3 in different cancers.