Fuses, either tube type or screw in, have metal bands in them that allow electricity to flow through the fuse and power the circuit. If the current flow through them is excessive, they will break and stop the flow of electricity. If you didn't have a fuse-or circuit breaker-the wires would overload, heat up and burn through or melt, probably causing a fire.

The wires to the outlets, switches and/or appliances are rated to carry a certain amount of amps. If the demand is higher then the fuse rating, the fuse will blow protecting the wire from overheating and causing a fire.

The fuse will also blow if there is a short in the wire.

Chuck

Also to protect your device from high current my be the sensitivity of your device is very high then it will be damage when the current flow is above the rating of sensitivity

Mr.Clever