If your vehicle is showing burning chemical or hot metal smell coming from the wheels, here are the most likely causes and the parts you'll need to fix each one.
A stuck brake caliper or seized slide pins cause the brake pads to constantly drag against the rotor. This generates extreme friction and heat, resulting in a strong burning metal or friction material smell.
Driving with the parking brake partially engaged, or having a rusted and seized parking brake cable, will cause the rear brake shoes or pads to drag and overheat.
New brake pads contain resins that cure and smell when first heated. Additionally, failing to clean the anti-rust shipping oil off new rotors during installation causes a distinct burning chemical smell.
A severely worn wheel bearing lacking lubrication will generate massive friction and heat. This burns the remaining grease inside the hub and emits a hot metal smell, usually accompanied by a loud hum or roar.
A leaking rear axle seal can allow gear oil to drip directly onto the hot brake rotors and pads, creating a strong burning chemical or sulfur-like smell as the fluid burns off.