Mercury holds the record among pure metals, melting at just −39°C (−38°F), which means it’s already liquid at room temperature. But several other metals also melt at surprisingly low temperatures, some warm enough to liquefy in your hand. These metals span the periodic table and show up in applications from electronics cooling to flexible robotics.
Metals That Melt Below 100°C
Six pure metallic elements melt at or below 100°C (212°F). In order from lowest to highest melting point:
- Mercury (Hg): −39°C (−38°F). The only metal that’s liquid at standard room temperature.
- Francium (Fr): ~27°C (81°F). Extremely rare and radioactive, so it has no practical use.
- Cesium (Cs): 28.5°C (83°F). Soft enough to cut with a knife, and it reacts violently with water.
- Gallium (Ga): 29.8°C (86°F). Will melt in your palm from body heat alone.
- Rubidium (Rb): 39.6°C (103°F). Another highly reactive alkali metal.
- Potassium (K): 63.4°C (146°F). Familiar from chemistry class for its explosive reaction with water.
Of these, only mercury and gallium are safe and stable enough for everyday applications. Cesium, rubidium, and potassium are alkali metals that react aggressively with moisture and air, making them impractical outside of specialized lab settings. Francium is so radioactive that no visible quantity has ever been collected.
Mercury: The Only Room-Temperature Liquid Metal
Mercury is dense, silvery, and completely liquid at 20°C, with a density of 13.5 grams per cubic centimeter, roughly 13.5 times heavier than water. That combination of fluidity and weight made it useful for centuries in thermometers, barometers, and electrical switches.
The major drawback is toxicity. Mercury releases vapor at room temperature, and those fumes accumulate in the body over time. It also forms fat-soluble compounds that pass through skin and tissue barriers, making even small spills a health concern. Most consumer products have phased out mercury in favor of safer alternatives.
Gallium: Melts in Your Hand
Gallium is the low-melting metal you’re most likely to encounter in videos and science demonstrations. At 29.8°C, it melts just below body temperature, so holding a chunk of it will turn it into a shiny puddle in your palm. Unlike mercury, gallium forms stable oxides on its surface and doesn’t release toxic vapor. Your body can excrete small amounts without harm, which is why it’s become the go-to “safe liquid metal” for demonstrations and research.
Gallium also has an unusual property: like water, it expands slightly when it solidifies. That means you can’t store liquid gallium in a rigid sealed container and let it freeze, or the expanding solid could crack the container. It also has one of the widest liquid ranges of any element, staying liquid all the way up to about 2,204°C before it boils.
Low-Melting Alloys
Mixing metals together can push the melting point even lower than either metal alone. These blends, called eutectic alloys, are where low-melting metals find most of their real-world applications.
Galinstan is the most well-known example. It’s a mixture of gallium, indium, and tin that melts at roughly 10°C (50°F) and can remain liquid down to about −10°C through supercooling. Because it’s liquid well below room temperature and non-toxic, galinstan has replaced mercury in many thermometers. It’s also being developed as a deformable conductive element in stretchable electronics and soft robotics, where circuits need to flex and bend without breaking.
Field’s metal is another common option, made from 51% indium, 32.5% bismuth, and 16.5% tin by weight. It melts at about 62°C (144°F), hot enough to stay solid at room temperature but low enough to liquefy in boiling water. It’s used as a liquid metal coolant in advanced reactor designs and in precision molding applications where you need a metal that flows easily and solidifies without shrinking.
Why Low Melting Points Matter
The practical value of these metals comes down to one thing: they can absorb and release heat at temperatures close to where humans live and work. That makes them useful as phase-change materials, substances that soak up energy when they melt and release it when they solidify.
In electronics cooling, low-melting metal alloys can pull heat away from processors in smartphones, USB flash drives, and other compact devices far more effectively than traditional wax-based phase-change materials. Metals conduct heat roughly 100 times better than paraffin wax, so even a thin layer can manage significant thermal spikes. They also maintain low vapor pressure during phase transitions, which means they won’t outgas or create pressure buildup inside sealed electronics.
Beyond consumer devices, these alloys are being explored for solar energy storage, industrial waste heat recovery, and building climate control. The idea is the same in each case: the metal melts as it absorbs excess heat, then releases that stored energy gradually as it resolidifies, smoothing out temperature swings without any moving parts or electricity.
Metals Just Above the 100°C Mark
If you expand the range slightly beyond 100°C, a few more familiar metals enter the picture. Indium melts at 157°C, tin at 232°C, and bismuth at 271°C. These aren’t “low” in the everyday sense, but compared to iron (1,538°C) or tungsten (3,422°C), they’re remarkably accessible. Tin’s low melting point is exactly why it’s been used in solder for thousands of years. Bismuth, combined with indium and tin, forms the basis of many lead-free fusible alloys used in fire sprinkler systems and safety plugs, where a predictable melting temperature triggers a mechanical response.