Is required not only for elongation of protein synthesis but also for the initiation of all mRNA translation through initiator tRNA(fMet) aminoacylation. ATP + L-methionine + tRNA(Met) = AMP + diphosphate + L-methionyl-tRNA(Met) Binds 1 zinc ion per subunit. Homodimer. Belongs to the class-I aminoacyl-tRNA synthetase family. MetG type 1 subfamily.