When the two terminals of a battery are connected directly with a wire there will be a low resistance path for the current to flow. The wire will get heated a little bit (depends on the diameter of the wire less the diameter more heat) and the battery will be quickly discharged. During depletion, it may become very hot, emit gasses, and possibly explode. The shorting wires will draw heavy current that may melt the wire or even cause them to soften and break.