What elements are car bumpers made from?
Chromium and steel
Car bumpers are made from reaction injection molded polyurethane plastic or Thermoplastic Olefins. Polypropylene foam is usually found inside bumpers to absorb impact during a collision, while better bumper systems may have hydraulic shock absorbers as well to provide extra protection. Unless you have an old car then it is made of steel.
The overwhelming majority of vehicles are made mostly of steel. However most front bumpers are made of vinyl ester resin and rear bumpers are made of urethane and other body panels can also be made of a form of plastic resin. Some sports cars such as the Chevrolet Corvette are made of fiberglass. Aluminum is also used for some body parts. And very expensive cars sometimes use carbon fiber in construction of the body.
If you hit a car by accident, it will do the damage to the bumper but not to your engine or any other part of the car. Bumpers are tough, and only help on small crashes, but in extreme crashes they won't do much help. They're just a little extra shield protection. They can also be used to pull a car, or get pulled in case you get stuck in mud or in really deep…
Steel, fiberglass, carbon fiber, stainless steel, plastic, rubber. Depending on what manufacturer, 'trim' of car, and what body part. For example a car often has steel doors, (safer in a collision..... if you got hit would you not want to be sitting inside a steel door?), and fiberglass or plastic bumpers
If the rear bumper of your car is detached a little bit is there any kind of glue or Super Glue which will work to hold it on?
This varies for every car made. One easy way to tell if it is aluminum or not is to use a magnet. Aluminum is not magnetic. Common parts made of aluminum are the radiator, intake manifold, cylinder heads, engine block, transmission case and/or bellhousing, heater core, bumpers, decorative trim, wheels, etc. Not all vehicles are equipped with all or any of these aluminum parts, however.