Current drawn by a permanent magnet DC motor
As the motor spins, the magnetic field induces back EMF in the windings. The induced voltage has opposite polarity than the supply voltage. Theoretically, when no load is present, these voltages cancel out and no current can flow.

When the motor is loaded and slowed down, the BEMF voltage decreases and allows more current to flow. When the motor is stalled, there is no BEMF and current is limited only by winding resistance.