1. "The White House announced a new policy." Here, "The White House" stands in for the President of the United States and their staff. The White House is a physical location, but it represents the power and authority of the presidency.
2. "He's got a lot of silver." "Silver" refers to money, not the actual metal. This is a common metonymy, often using precious metals to represent wealth.
3. "She's studying the classics." "Classics" refers to works of ancient Greek and Roman literature. The term represents a whole body of work, rather than just a specific text.