An object's properties are characteristics that delineate it from other objects. Properties can be anything from composition to color to ductility. Without knowing an object's properties, it is impossible to characterize it. For example, looking at some common properties of metals helps to differentiate them from non-metals or metalloids.
Metals are electrically and thermally conductive, malleable, ductile and possess luster. They also have plastic deformity, meaning that any distortion in shape remains until otherwise changed. Objects that meet all of these criteria are classified as metals. To further classify a metal, a table can be made that contains all of the above characteristics, and they can be grouped by other methods. For example, a list of metals can be made, listed from most conductive to least conductive. Metals may also be grouped by color or hardness. Other properties include chemical reactivity or tensile strength.
The properties of other materials aid in classification. For example, the Mohs scale of mineral hardness groups minerals on a scale of one to 10 by testing what materials that they can scratch without suffering damage, ranging from talc at level one to diamond at level 10. When classifying objects, it i's best to have some common ground between all of them in order to better group them.