Margin trading allows investors to borrow funds from their brokerage to purchase securities, amplifying both potential returns and potential losses through financial leverage.

When you buy stocks on margin, you're essentially using your existing portfolio as collateral to borrow additional capital, typically up to 50% of the purchase price for most stocks (as regulated by Federal Reserve Regulation T).

While this leverage can magnify profits—a 10% gain on a stock purchased with 50% margin becomes a 20% return on your invested capital—it equally magnifies losses, and comes with significant risks that many novice investors underestimate.

The mechanics of margin involve several critical concepts: the initial margin requirement (typically 50%), which determines how much you can borrow; the maintenance margin (usually 25-30%), which is the minimum equity percentage you must maintain; and margin calls, which occur when your equity falls below the maintenance requirement, forcing you to either deposit additional funds or have securities sold to cover the shortfall.

Perhaps the most dangerous aspect of margin is that losses can exceed your initial investment—if a stock purchased with 50% margin declines by 50%, you've lost your entire equity contribution while still owing the full loan amount plus interest.

Margin interest rates, typically ranging from 6-12% annually depending on the borrowed amount and brokerage, add ongoing costs that erode returns and create a hurdle rate your investments must exceed to remain profitable.

Professional traders use margin judiciously as a short-term tactical tool, maintaining significant unused margin capacity as a buffer and closely monitoring positions to avoid margin calls.

In contrast, retail investors often misuse margin by remaining continuously leveraged, failing to account for margin interest, and holding leveraged positions through volatile periods where even temporary price swings can trigger devastating margin calls.

The 2008 financial crisis and the 2020 GameStop volatility demonstrated how margin amplifies market stress—investors forced to sell during market declines due to margin calls create downward spirals that accelerate losses.

Before using margin, investors should have substantial trading experience, maintain emergency liquidity for potential margin calls, and understand that leverage is a double-edged sword that demands respect, discipline, and rigorous risk management.