What might be the cause of a metal on metal scraping noise that your 95 Nissan Maxima makes most of the time when moving?

Worn out disc brake pads. It should not be scraping anything... Listen to find out if the scraping noise is proportional to the speed that you are going at. Roll down your Windows and have someone else also listen to hear which tire or area of the car it is coming from. Look under the car and see if anything undercarriage has rusted or is falling off and touching somthing - like the ground - or wheels. When was your brake pads changed?? It may be the scraping noise of the brake pads wear indicator - a small metal piece that touches the brake rotor when the pad is too far worn. You can also check them yourself by removing the tires and looking at the wheel perpendicularly in the "peep" area where you can see the brake pads - there should be at least a few millimeters (say 1/8"or more of the pad material attached to the metal pad) So when you are looking make sure you are looking at the actual pad material and not the metal backing. Also check to see that the metal shields on the inside of the front brake disks are not rubbing on the disks. If they are, simply bend them away from the disks slightly. Leave about 1/2 inch of clearance. Also check you wheel bearings by putting the car on jackstands so front tires are off the ground, grab the tire at the 12 and 6 position and try to wobble the tire. If it moves up and down then the bearing are bad.