Methylzinc chloride is primarily used in organic synthesis as a methylating agent. It is particularly valuable in the preparation of organozinc compounds, which are intermediates in various chemical reactions. This compound is often employed in cross-coupling reactions, such as the Negishi coupling, where it facilitates the formation of carbon-carbon bonds between different organic molecules. Additionally, it is utilized in the synthesis of complex organic molecules, including pharmaceuticals and fine chemicals, due to its ability to introduce methyl groups efficiently. Its role in polymerization processes is also notable, where it acts as a catalyst or co-catalyst in the production of specific polymers.