Banks collect deposits and make loans, earning the spread between deposit rates and lending rates (net interest margin). The four largest US banks — JPMorgan, Bank of America, Wells Fargo, and Citigroup — collectively hold trillions in assets and dominate investment banking, commercial lending, and consumer finance. Bank profitability is directly tied to the Federal Reserve's interest rate policy, credit quality cycles, and loan demand from consumers and businesses.
Net Interest Margin (NIM) is the key profitability metric — rising rates typically expand NIM. Watch loan loss provisions for early credit cycle warnings. Investment banking revenue from M&A and IPO pipelines indicates deal-making confidence.