You can classify a metal: when a subject can surely conduct electricity.
examples: if a problem says the unknown object is malleable, or says "on the left side of the periodic table", is a conductor, is shiny, etc.
Metalloids: when a subject is alongside the staircase, uses word "semi-conductor", it depends on if it's malleable or ductile, and depends on whether it's shiny or not, etc.
Nonmetal: is located on the right side of the periodic table, can ONLY be an insulator, is not malleable, is not shiny, etc.
