It is believed to be the first compound to have formed in the universe, and is of fundamental importance in understanding the chemistry of the early universe. This is because hydrogen and helium were almost the only types of atoms formed in Big Bang nucleosynthesis. Stars formed from the primordial material should contain HeH, which could influence their formation and subsequent evolution. In particular, its strong dipole moment makes it relevant to the opacity of zero-metallicity stars. HeH is also thought to be an important constituent of the atmospheres of helium-rich white dwarfs, where it increases the opacity of the gas and causes the star to cool more slowly.
HeH could be formed in the cooling gas behind dissociative shocks in dense interstellar clouds, such as the shocks caused by stellar winds, supernovae and outflowing material from young stars. If the speed of the shock is greater than about , quantities large enough to detect might be formed. If detected, the emissions from HeH would then be useful tracers of the shock.
Several locations had been suggested as possible places HeH might be detected. These included cool helium stars, H II regions, and dense planetary nebulae, like NGC 7027, where, in April 2019, HeH was reported to have been detected.