If your vehicle is showing metal-on-metal scraping sound from the center of the vehicle, here are the most likely causes and the parts you'll need to fix each one.
The thin metal heat shield above the exhaust has rusted around its mounting points and dropped down. It is now scraping against the rotating driveshaft or vibrating against the exhaust pipe.
Failed rubber exhaust hangers allow the exhaust system to sag and scrape against the vehicle's crossmember, driveshaft, or the ground. This frequently happens if an aftermarket exhaust was recently installed and improperly aligned.
On rear-wheel or all-wheel drive vehicles, the bearing that supports the middle of the driveshaft can fail. When the rubber isolator tears, the driveshaft sags and scrapes against the metal bearing bracket while driving.
The needle bearings inside the driveshaft's universal joints have dried out and deteriorated. This causes a rotational scraping, squeaking, or clanking sound from the center or rear of the vehicle that increases with vehicle speed.
In manual transmission vehicles, a worn clutch release (throwout) bearing will cause a harsh scraping or grinding noise from the center-front of the vehicle. This noise typically changes or only occurs when the clutch pedal is pressed.
In 4WD or AWD vehicles, a stretched internal drive chain can scrape against the inside of the transfer case housing, or internal bearings may have failed due to fluid loss.