Rubidium is a soft, silvery-white metal at room temperature. Its melting point is only around 40º C, so it's possible for it to melt on a hot day, or if squeezed in the hand. That makes it one of the few metals that can be a liquid in a natural environment (Mercury has the lowest temperature needed to become liquid, and is liquid at room temperature).
Chemical properties:
Rubidium is one of the most reactive elements in the periodic table. It's actually the 2nd most reactive metal element (after Caesium). It will spontaneously ignite in air (forming some of its oxides) and reacts violently with water (producing rubidium hydroxide and hydrogen gas, which is immediately ignited). The flames are a yellowish-purple color. Because of its reactivity, rubidium has to be stored in either kerosene, nitrogen gas, or in a vacuum bottle.