Why are bells made of metals?

Why are utensils made up of aluminium and brass?

Why are tyres made of rubber not of steel?

Why are springs made of steel & not of copper ?

Calorimeters are made of metals not glass. Why?

Why are alkaline earth metal smaller than the Corresponding alkali metals.

Why are wheels of automobile made circular

At an airport, a person is made to walk through the doorway of a metal detector, for security reasons. If she/he is carrying anything made of metal, the metal detector emits a sound. On what principle does this detector work?