Used primarily in organic synthesis as a powerful methylating agent, especially for the methylation of heteroatoms such as oxygen, nitrogen, and sulfur in various substrates. It is particularly effective in converting phenols to methyl ethers, carboxylic acids to methyl esters, and amines to methylammonium salts under mild conditions. Its high reactivity and selectivity make it valuable in pharmaceutical and fine chemical manufacturing where precise methylation is required. Due to its thermal instability, it is often handled at low temperatures and in anhydrous environments to ensure safety and optimal performance.