1, Metals are opaque, lustrous elements that are good conductors of heat and electricity. 2, Plastic is any synthetic or semi-synthetic organic polymer. 3, Ceramics are all around us. This category of materials includes things like tile, bricks, plates, glass, and toilets. 4, A glass is an amorphous solid. The term is usually applied to inorganic solids and not to plastics or other organics. These four are the majority ordinary types.