For domestic wiring to be as safe as possible it needs the correct thickness of wire to be used and the correct amperage fuse to be used. If you use a fuse of higher amperage than the circuit is designed for, then the wire could melt and set on fire or the appliance can be seriously damaged.
Fuses are rated in Amperes or Amps as they are more commonly known, a fuse is a deliberate weak link in a circuit and will melt if too much current passes through the fuse. There are several different types of fuse but they all do the same thing which is to protect the circuit. A fuse will not stop you from being electrocuted! But a fuse can help prevent electrical fires.