The methylium cation () exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of the  cation, and this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives an electrophilic methylating reagent that reacts by the S2 pathway:
Similarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they readily undergo S2 reactions by weak nucleophiles.
The methyl cation has been detected in interstellar space.