tips for buying a metal detector
Compare the feature list to the requirements of the task to be done: Does it need to be waterproof? What's the working range and sensitivity? Is the power supply standard batteries like your other tools? Do you need an audible or visual indicator? Choose a size to match your needs for portability, in a toolkit or trunk. Choose a form to match the application; small for indoors, a wand for on the beach, or mounted for a passage or conveyor. Test it or a similar model if possible.
The top consideration is to decide on your budget. The budget should include the cost of the metal detector and associated accessories such as a headphone, digging tools like trowels or beach scoops. You may also consider others, like coil cover and a metal detector bag.