What the Foam Is Protecting
A metal detector is tough where it meets the ground and fragile where the electronics live: control box, display, and connectors. Loose in a trunk, the machine slides on every stop, and the corner it lands on is never the shaft. Closed-cell foam absorbs those hits and spreads the load so the impact never reaches the housing or the screen. Coils are tougher, but the ears and cable strain relief on a spare coil crack exactly the way you would expect when something heavy lands on them. A padded bag turns all of that from luck into routine.
Soft Bag, Backpack, or Hard Case
A padded soft bag is the everyday answer: detector broken down, coils and chargers in the side pockets, safe in a trunk or truck bed and stored clean between hunts. A padded backpack does the same job while leaving both hands free for a long walk-in. The hard cases are for trips where the bag leaves your hands: airline travel, shipping a machine, or a rig that lives behind the seat of a work truck. Flying is the bright line. Checked baggage handling is exactly the abuse a rigid shell and fitted foam were designed for, and a hard case is the only version of your detector's flight you never have to think about.
Match the Case to the Machine
The more detector you carry, the stronger the case for padding; a flagship machine riding bare in a trunk is a risk nobody needs to take. Check the collapsed length of your detector against the bag before buying: universal bags fit most machines with the shaft broken down, while brand bags are cut for their own models. Most of these have room for a spare coil and the small parts and accessories that travel with it, and if the machine itself is still on the shortlist, start at metal detectors. Field pouches, belts, and holsters skip the foam on purpose; those live under field pouches and covers, and everything together is in all bags, pouches and covers.