Mercury is a metallic element that occurs in liquid state at room temperature. The vapour pressure over liquid mercury is already high at room temperature. To inhale air with mercury vapour is very hazardous for the health.
Mercury is in liquid phase down to -38,87 °C and the boiling point is 356,58 °C, lower than any other metallic element.
Mercury has been used in all kinds of products from thermometers, batteries to teeth fillings.