No.Sunglasses are made up of a frame and a pair of light-filtering lenses.Most of the lens are made of colorized plastic, such as polycarbonate.Glass is also used for the high quality brands.Sunglass frames are usually made from metal or plastic.
I can see from your words that you are not quite familiar with sunglasses. So, as a matter of fact, on a worldwide basis. sunglasses are made of different materials, there are metal sunglasses , plastic sunglasses, as well as mixed materials sunglasses. But all of them serve to better protect your eyes from harmful lights. Maybe you should pay more attention to the lenses which could decide the effectiveness of the sunglasses. Hope you find what you seek.
Of course not all the sunglasses are made by plastics. Some sunglasses lenses are made by glass or plastics. The frames of sunglasses can be made by metal or plastics. But the plastic sunglasses are very popular nowadays because they are less expensive compared with the sunglasses made by other kind of materials. I know that ray ban sunglasses are made by glass. Different kinds of material has its own advantages and disadvantages. The glass sunglasses are easy to be broken. But it is said that glass sunglasses usually have visible light transmission levels of 15% to 20%.
I bought a pair of glass sunglasses last week. The lenses are made by glass. The salesman told me that the color in glass lenses will last forever. And they are also scratch resistance. This kind of lenses can provide clearer vision and better filtration. Glass lenses are also more chemical resistant. But glass lenses are heavier than plastic lenses. Besides, if you have high prescription, the lenses will be thinner or thicker in some areas, which will lead to lighter and darker areas across the lenses.