Lets try a water analogy. Water pressure is volts. Water flow is amps. The faucet is the load resistance. Thus no matter how many gallons are available, the only amount of water that will flow is determined by the water pressure (volts) and the amount the faucet is open (resistance).
Thus it doesn't make any difference how much current the supply can output, the actual current is determined by the voltage and the load resistance. (And the power output is volts times amps).
Does that make sense?