A thread or slender rod of metal. Wire is usually circular in cross section and is flexible. If it is of such a diameter or composition that it is fairly stiff, it is termed rod. The wire may be of several small twisted or woven strands, but if used for lifting or in a structure, it is classed as cable. Wire may be used structurally in tension, as in a suspension bridge, or as an electrical conductor, as in a power line. The working of metal into wire greatly increases its tensile strength. Thus, a cable of stranded small-diameter wires is stronger as well as more flexible than a corresponding solid rod. Wire may be treated or coated with various substances to protect it from corrosion or environmental influences. In addition, electrical conducting wire is usually covered with insulating material.