Answer: Mercury

When it comes to metals, mercury is quite a curiosity. Most metals have a melting point that is in the hundreds or thousands of degrees (copper melts, for example, at 1,984.32F). Mercury on the other hand has a melting point of -37.89F; as long as it is warmer than that very chilly temperature point it remains liquid.

To understand why mercury has such an incredibly low melting point that it remains liquid at room temperature (and even in the depths of winter nearly everywhere but extreme winter climates like the Arctic Circle) we need to approach it from an atomic level. The melting point of a metal is related to the structure of the electron bonds between the atoms that comprise the metal. Metal with a very high melting point (such as tungsten’s fiery 6,192F melting point) have very strong bonds between the atoms and it takes an enormous amount of energy to break down those bonds and change the metal from a solid to a liquid.

By comparison, the bonds between atoms of mercury are very weak and it takes very little energy to break them down and change the metal from a solid to a liquid. So little, in fact, that we end up with a metal that liquefies in the presence of even the most minute amounts of heat energy and requires extreme cold to solidify.