The Linear Momentum Indicator is a useful and free Forex indicator for MT4. The indicator calculates the difference between the current closing price and the closing price of a certain number of periods ago. The result is then plotted as a histogram, which helps traders identify the direction and strength of the momentum. The histogram is color-coded to indicate whether the momentum is positive or negative. By tracking the changes in the histogram, traders can use the Linear Momentum Indicator to identify the trend and potential trading opportunities.