The field of m6A modification and epitranscriptomics has recently attracted much attention. More methods allowing for precise m6A site profiling and location are developed and crucial players of m6A modification machinery are increasingly identified. Although some challenges remain, m6A modification is found to modulate almost all aspects of RNA metabolism, such as splicing, stability, structure, translation, and export. Thus, m6A modification adds a new layer of post-transcriptional gene expression regulation, and it is implicated in T cell response to HIV infection, type I interferon production, and T cell differentiation and homeostasis. Moreover, evidence supporting its involvement in various human diseases including cancers is accumulating. Given the role of m6A modification in gene expression regulation and immune response, it invites the speculation that m6A modification may justify the pathogenesis of systemic lupus erythematosus (SLE) and take part in the initiation and progression of SLE. In this review, we introduce the widespread existence of m6A modification and briefly discuss components of m6A modification machinery in mammals. We mainly summarize the studies reporting the mechanisms of m6A modification in gene expression regulation through modulating pre-mRNA splicing, mRNA stability, RNA structure, translation, and pri-miRNA processing. Biological functions related to immune response of m6A modification and the implication of m6A modification in cancers are highlighted. In the end, we surmise the potential link between m6A modification and SLE.