Other forms: silver screens
The movie industry is sometimes called the silver screen. In the early days of film, a silver screen was a specific type of screen onto which films were projected.
As a general term for the movies, silver screen is a figure of speech called a metonym, a word that comes from an object closely associated with it. In this case, the silver lenticular screen was made from either woven silk and other fabrics or sheets coated with silver dust, and used with the earliest projectors. These metallic screens are old-fashioned, and so is the broader term for the entire cinema industry.