Key Takeaways The S&P 500 added 0.3% on Tuesday, Sept. 24, as a report showed a slump in consumer confidence and China unveiled an economic stimulus package.Shares of mining giant Freeport-McMoRan soared as copper prices jumped following Beijing's monetary policy announcement.

Wall Street's main indexes were set for a subdued open on Tuesday, as investors scoured for clues on what the Federal Reserve's next policy move might be, while commodity stocks got a boost after China unveiled a bumper stimulus package.

Wall Street saw modest gains as mining stocks rallied on China’s new stimulus measures, while a drop in consumer confidence and Fed uncertainty tempered broader market advances.