Margin is the portion of your own funds required to open a position when using leverage. Rather than paying the full value of a trade, you put down a smaller deposit — the margin — while the rest of the position size is supported by leverage. Margin is not a fee; it is held as security while the trade is open. If the market moves against the position, more margin may be required to keep it open. Understanding margin is essential because it is directly tied to leverage and to how much risk a trader is really taking on.