${\mathrm{C}}_6{\mathrm{H}}_6+{\mathrm{CH}}_3\mathrm{Cl}\to {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_3+\mathrm{HCl}$ 

The above reaction is an example of

 The $\mathrm{Friedel}-\mathrm{Crafts}$ alkylation reaction, an electrophillic aromatic substitution process, can add an alkyl group to a benzene molecule. One illustration is the insertion of a methyl group to a benzene ring. The electron from the benzene ring attacks the electrophile to create a nonaromatic carbocation.