Methanol ($CH_3OH$) molecules are held together primarily by intermolecular hydrogen bonds due to the presence of a highly electronegative oxygen atom covalently bonded to a hydrogen atom. During the phase transition from liquid to gas (vaporization), the thermal energy supplied is used to overcome these strong intermolecular hydrogen bonds. Although dipole-dipole interactions and London dispersion forces are also present, hydrogen bonding is the dominant and strongest intermolecular force. Covalent bonds are intramolecular forces and remain intact during physical phase changes like vaporization.