Epitranscriptomics is the field of research studying the collective epigenetic modification of RNA, affecting all aspects of the RNA fate after transcription through post-transcriptional regulation. These chemical modifications add an additional layer of information beyond the one transcribed in the genetic sequence, allowing organisms to have a higher level of fine-tuning transcriptional and biochemical responses that surpass simple gene activation or repression. Of these modifications, the deposition of a methyl group at different residues in the backbone of RNA nucleosides (RNA methylation) is the most abundant and most studied. In this chapter, we provide a state-of-the-art overview of known RNA methylation modifications in animals and plants, drawing a parallel between the two systems and highlighting the current knowledge gaps of plant models. Centering on RNA methylation in plants, this chapter will focus on the best characterized modifications to date, N6-methyladenosine and 5-methylcytidine of plant mRNAs, specifically dissecting their molecular dynamics and distribution, as well as their role in environmental adaptations, mRNA life cycle, transcription, and chromatin regulation.