Among the elements grouped as metals, mercury has the lowest melting point at minus 38.83 degrees Celsius. Mercury has a very wide temperature range in its liquid state, according to Jefferson Lab, with a boiling point of 356.73 degrees Celsius.
There exists a group of metal alloys that are valued by metallurgists and industry for their overall low melting points. These fusible metals are often used in thermometers and for certain medical applications. One fusible metal is an alloy of three alkali metals, cesium, potassium and sodium. According to Wikipedia, this alloy has a melting point of only minus 78.2 degrees Celsius.