The carbon atom is left with either one or three unpaired electrons (unsatisfied valence bonds), depending on the molecule's excitation state; making it a radical.

Methylidyne is a highly reactive gas, that is quickly destroyed in ordinary conditions but is abundant in the interstellar medium (and was one of the first molecules to be detected there).

Following the substitutive nomenclature, the molecule is viewed as methane with three hydrogen atoms removed, yielding the systematic name "methylidyne".

[5] Reactions of the doublet radical with non-radical species involves insertion or addition: whereas reactions of the quartet radical generally involves only abstraction: Methylidyne can bind to metal atoms as tridentate ligand in coordination complexes.

In October 2016, astronomers reported that the methylidyne radical ⫶CH, the carbon-hydrogen positive ion :CH+, and the carbon ion ⫶C+ are the result of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovas and young stars, as thought earlier.