A guide wire combined with a catheter or medical device for moving through a body lumen to a desired position in the body with the aid of an applied magnetic field. The guide wire is provided with a magnet on its distal end that can be oriented or oriented and moved by the application of a magnetic field to the magnet. A catheter or other medical device can be advanced over the guide wire. Once the medical device is in its desired position, the magnet can be withdrawn through the lumen of the catheter. Alternatively, a guide wire with a magnet on its distal end can be docked at the distal end of a catheter or medical device and can be oriented, or oriented and moved by the application of a magnetic field.