Net margin is a useful metric. It tells you how much profit remains after costs, interest, and tax are deducted from revenue. But it does not tell you whether the sector is structurally tough. It does not tell you whether management has pricing discipline. It does not tell you whether the company has survived a crisis that killed competitors. It does not tell you whether the business can reinvest. It does not tell you whether low margin is a weakness or simply the price of operating in a hard but defensible industry. It does not necessarily tell you whether the stock is worth picking up in the market.