Used as a powerful methylating agent in organic synthesis, particularly for the methylation of aromatic and heteroaromatic compounds, phenols, and carboxylic acids. It is highly effective in introducing methyl groups under mild conditions, making it valuable in pharmaceutical and agrochemical research. Due to its high reactivity, it is often employed in the preparation of quaternary ammonium salts and in catalytic reactions involving transition metals. Its ability to function in non-aqueous environments makes it suitable for sensitive substrates. However, it must be handled with care due to its toxicity and moisture sensitivity.