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.