This past week I was out of town once again, having to teach a class. The next day a friend drove to the town I was at and asked if I could provide to him some metal detector training. I always have a metal detector in the work truck so of course I could provide some training on the use of the machine.
Metal detectors have been in use for over 100 years now. Initially they were very large and not very convenient to use. They were used during WWII to clear mine fields. Metal detectors came into more widespread, civilian use in the 50s and 60s. With the advent of the computer age, metal detectors are widely available in all price ranges ($55 to thousands) and with varying capabilities.
There are also small palm sized detectors that are used by waiving over someone you have captured to determine if they have a gun, knife, razor, or needle on their person. I don't own one of these, mine is the large model used for locating items under ground. Many years ago I purchased my metal detector from Kellyco http://www.kellycodetectors.com/indexmain.php . They have excellent customer service since the employees are all metal detector enthusiasts. They can answer any questions you have, including suggesting which metal detector would be best for you in the price range you want to spend.
I use my metal detector to find metal. Duh. What am I looking for? All kinds of things, especially when using it for work. For personal use I find fencing, coins, nails, etc. In a survivalist situation a metal detector can be used for finding buried caches of weapons and ammunition, buried containers, cement vaults (with rebar), and of course coins.
I don't think buying a metal detector would be number one on my list of survival products but it is something of great value. How often do you read about items being cached? Can you find something that you cached? With a metal detector you may be able to!