Mercury is a silvery-white liquid post-transition metal. The reason for mercury being a liquid is complex. It is heavy; a chunk of iron can float on mercury. Compared to other metals, it does not conduct heat well. However, it conducts electricity fairly well. Mercury is the only metal with a known melting point (−38.83 °C) lower than caesium. Mercury is one of the two elements that are liquids at standard temperature and pressure. Bromine is the other one.