metal detector 
noun
An electronic device that gives an audible or other signal when it is close to metal, used for example to search for buried objects.If I'm not allowed to carry a cell phone through the metal detector, fine....
- On Monday of last week Thomas, his father Pat, and friend Bernard used a metal detector in their search.
- In September they returned, each armed with a metal detector, and searched the field after the farmer took out his crop.
- long-playing
- long primer
- long-range
- Long Reed
- long reins
- long-running
- long s
- long service leave
- long-serving
- Longshan
- longship
- longshore
- longshore drift
- longshoreman
- long shot
- long sight
- long-sighted
- long-sightedly
- long-sightedness
- long-sleeved
- long-sleever
- longspur
- long-standing
- long-stay
- Long, Stephen Harriman