Fuse wire is a safety device connected in an electric circuit in a series connection with the live wire. It has high resistivity and low melting point so that it would allow current up to its safe limit to pass through it, but if excess current flows it will melt and blows off thus breaking the circuit and prevent any hazards from short-circuiting and it also prevents the costly electrical appliances like geyser, toaster, microwave, etc. from getting damaged.