The general properties of metals and nonmetals are distinct. Not all the metals and nonmetals possess all these properties, but they share most of them to varying degrees.
Metalloids show some properties that are characteristic of both metals and nonmetals. Many of the metalloids such as silicon, germanium and antimony act as semiconductors which are important in solid state electronic circuits. Semiconductors are insulators at lower temperatures but become conductors at higher temperatures. The conductivities of metals by contrast decrease with increasing temperature
Aluminum is the least metallic of the metals and is sometimes classified as a metalloid. It is metallic in appearance and an excellent conductor of electricity.
The elements that border the metals and the nonmetals are metalloids. The metalloids or semi metals have properties that are somewhat of a cross between metals and nonmetals. They tend to be economically important because of their unique conductivity properties, which can make them valuable in the semiconductor.