Metalloids do not conduct heat and electricity as well as metals, but otherwise, they display some of the properties of metals and some properties of nonmetals. The majority of all elements are metals, and metalloids are in between metals and nonmetals in terms of characteristics.
Metals, except for mercury, are in a solid state at room temperature. Metals are always of high luster, while metalloids may be either dull or shiny. Metals have a metallic appearance and are good conductors of heat and electricity. Metalloids are usually capable of conducting, but even when they are, they do not conduct as well as metals.
Metals are always malleable, while metalloids are usually, but not always, malleable. Metals lose electrons in reactions, while metalloids can either gain or lose electrons. Metals are always ductile, while metalloids are usually ductile.
Metals are usually dense, often have a high melting point and corrode or oxidize when exposed to air or sea water. Metalloids often exist in several forms and typically make good semiconductors. Nonmetals are essentially the opposite of metals and have the nonmetal characteristics of metalloids. They are usually dull, brittle, not malleable or ductile, much less dense than metal, and bad conductors of heat and electricity. They have low melting points and usually gain electrons in reactions.