Enables mRNA (N6-adenosine)-methyltransferase activity. Involved in several processes, including RNA metabolic process; forebrain radial glial cell differentiation; and gamete generation. Located in nucleus. Part of RNA N6-methyladenosine methyltransferase complex. Is expressed in genitourinary system. Orthologous to human METTL3 (methyltransferase 3, N6-adenosine-methyltransferase complex catalytic subunit). [provided by Alliance of Genome Resources, Apr 2022]