Well, of course the melting point is pressure dependent, that's what you read out of a phase diagram:

https://wisc.pb.unizin.org/app/uploads/sites/293/2019/07/phase_diagram.png

As you can also see there, if the pressure gets low enough, it's no longer a melting temperature, but actually a sublimation temperature. The p-T-dependence is described by the Clapeyron equation: https://en.wikipedia.org/wiki/Clausius%E2%80%93Clapeyron_relation

Avinash Kumar Mehta

For most other substances (where the solid is more dense than the liquid) the effect is in the reverse direction (so that vacuum will lower the melting point), but the effect is still small, at least for the small pressure difference between atmospheric and vacuum.

Melting point of water decreases with increase of pressure and its boiling point increases with the pressure increase. For other materials, the melting point and boiling point increase with pressure increase.