Numerical simulations of high-pressure gas atomization are performed by varying the molten metal and the atomizing gas to understand the physics behind high-pressure gas atomization and the effects of the melt and the atomizing gas on droplet size distributions. The Volume of Fluid method is used in the OpenFoam platform. The three melt-gas combinations used in these simulations are aluminum-nitrogen, aluminum-argon, and low carbon steel-nitrogen. Three interfacial instabilities have been identified in the early stages of all three atomization processes. Comparison of aluminum and steel as the molten metal indicates that steel atomizes more effectively and provides a higher yield than aluminum. However, changing the atomizing gas does not result in a significant change in the atomization process.