A polymer is a substance made of many repeating units called monomers. Plastics are formed by many identical repeating monomers thus are polymers.

Glass is not a polymer substance. Glass is an amorphous solid that is primarily composed of silica (silicon dioxide). It is formed by cooling molten silicates rapidly, resulting in a non-crystalline, vitreous material. While glass is not a polymer, it is an important material used in various applications due to its transparency, hardness, and thermal properties.

Iron is not a polymer substance. Iron is a chemical element with the symbol Fe and is a metal. It is not composed of repeating monomers like a polymer; rather, it consists of metallic bonds between iron atoms in a crystalline structure. Iron and its alloys are widely used in construction, machinery, and many other applications due to their strength and ductility.

Polymers are giant organic molecules assembled from many smaller molecules called monomers. Polymers consist of many repeating monomer units in long chains, sometimes with branching or cross-linking between the chains.

Since plastic is also made up of a long chain, it is a polymer.

Copper is not a polymer substance. Copper is a chemical element with the symbol Cu and is a metal. Like iron, it consists of metallic bonds between copper atoms in a crystalline structure. Copper is an excellent conductor of electricity and is used in electrical wiring, plumbing, and many other applications.