The melting point of a substance is the temperature at which it changes from a solid to a liquid state. The reverse process of a liquid or gas state into a solid is the freezing point, which is the same temperature as the melting point. Keep in mind that pressure is also a key factor in state changes. For example, helium would require a pressure of over twenty times normal atmospheric pressure to freeze.
The coldest known object in the universe is the Boomerang Nebula, which measures in at the temperature of -458 °F (-272 °C).
The element hydrogen’s melting (or freezing) point comes close at -434.4 °F (-259.1 °C). Since hydrogen exists naturally as a gas, it requires immensely cold temperatures to condense it into a liquid. Liquid hydrogen is mainly used for rocket fuel for spacecraft. It has the lowest molecular weight of any known substance and burns with extreme intensity at 5,500°F. It requires extreme, technical care to store and handle hydrogen.
The temperature on the surface of the sun is 9,941 °F (5,505 °C).
The melting point of tantalum carbide comes the closest at 6,960 °F (3,850 °C). It is used in tool bits for cutting and is added to tungsten carbide alloys.
The chemical element with the highest melting point is tungsten at 6,177 °F (3,414 °C).
This property makes tungsten excellent to use as filament in light bulbs. Alloys made with tungsten are often used to make wear-resistant abrasives, cutting tools like knives and drills, and mining, milling, and turning instruments to be used in the metalworking, woodworking, mining, and petroleum industries.