Margin vs Leverage
Initial margin, maintenance margin, and effective leverage.
Margin is the amount of money required to hold a futures position. It is not the full value of the contract and it is not the same thing as risk. It is a good-faith deposit that allows you to control a much larger notional value.
Leverage is created because the contract value is much larger than the margin required. If one ES contract represents a large notional exposure and your broker only requires a fraction of that amount to enter, small price changes can create meaningful gains or losses. Leverage helps efficient traders, but it punishes careless sizing.
Never size a trade only because margin allows it. Your stop distance, dollar risk, account size, and daily loss limit matter more than the maximum number of contracts your platform will let you trade.