Methyltransferase-like 8 (METTL8) is a member of the methyltransferase-like protein (METTL) family, which typically utilizes S-adenosylmethionine (SAM) as a substrate to catalyze methylation. 3-methylcytidine (m3C) is a type of methylation that occurs at the third nitrogen atom of the cytosine base in RNA, playing a wide-ranging role in maintaining RNA secondary structure, stability, and function. METTL8 is currently the only enzyme known to regulate m3C modification in both messenger ribonucleic acid (mRNA) and transfer ribonucleic acid (tRNA). Additionally, METTL8 is closely associated with processes such as embryonic stem cell differentiation, skeletal muscle gene regulation, and tumor proliferation. Given the significant role of METTL8, this article focuses on the structural composition, functional characteristics, and research progress associated with METTL8, aiming to provide insights for further investigation into its biological functions.