Can I plug an external usb hard drive into the Apple TV for Movies

I have an Apple TV 2 with the latest aTV Black firmware 5.3.

Can I just plug an external usb hard drive into the Apple TV to play movies etc

No.   The micro USB port provided is not capable as acting as a host port (which is what is required to support a hard disk).  Its only purpose is to support loading of firmware on to the ATV.

Thanks for that.

i think you can only do this with the apple 1