RNA N6-methyltransferase that methylates adenosine residues at the N(6) position of a subset of RNAs and is involved in S-adenosyl-L-methionine homeostasis by regulating splicing of S-adenosylmethionine synthase transcripts (sams-3, sams-4 and sams-5) (PubMed:33930289). Able to N6-methylate a subset of mRNAs containing the 5'UACAGAAAC-3' nonamer sequence (PubMed:33930289). Plays a key role in S-adenosyl-L-methionine homeostasis: under rich-diet conditions, catalyzes N6-methylation of S-adenosylmethionine synthase mRNAs (sams-3, sams-4 and sams-5), directly inhibiting splicing and protein production of S-adenosylmethionine synthase (PubMed:33930289). In addition to mRNAs, also able to mediate N6-methylation of U6 small nuclear RNA (U6 snRNA) (PubMed:33930289). Required for gamete production, inhibiting germ cell proliferative fate and ensuring germ cell meiotic development (PubMed:19596901, PubMed:19752194). Also promotes progression of the mitotic cell cycle in those germ cells that continue to proliferate (PubMed:19596901, PubMed:19752194). Plays a role in the development of the vulva, somatic gonad and embryo (PubMed:19596901). an adenosine in mRNA + S-adenosyl-L-methionine = an N(6)-methyladenosine in mRNA + H(+) + S-adenosyl-L-homocysteine adenosine in U6 snRNA + S-adenosyl-L-methionine = H(+) + N(6)-methyladenosine in U6 snRNA + S-adenosyl-L-homocysteine Self-associates (PubMed:19752194). Interacts with dlc-1; the interaction is direct, and is required for nuclear localization of mett-10 (PubMed:19752194). Accumulates in nuclei as cells enter meiosis (PubMed:19596901, PubMed:19752194). During meiotic prophase, expression is predominantly nuclear, but does not co-localize with DNA (PubMed:19596901). Recruited to the nucleus by dlc-1, a component of the dynein complex (PubMed:19752194). Expressed in the intestine, vulva, and cells of the somatic gonad including distal tip cells, gonadal sheath cells and spermatheca. Belongs to the methyltransferase superfamily. METTL16/RlmF family.