The metal that is heavier than water is mercury. Mercury is a unique element, known for being the only metal that is liquid at room temperature. Its high density, approximately 13.6 grams per cubic centimeter, makes it considerably heavier than water, which has a density of about 1 gram per cubic centimeter. Mercury's distinct physical properties have made it useful in various applications, including thermometers, barometers, and certain types of electrical switches. However, due to its toxic nature, the use of mercury is now heavily regulated, and alternatives are often sought in many of its traditional applications.