Freezing rain is the term given to the precipitation of the rain sustained at temperatures below freezing by the ambient air mass, which results in freezing on encountering with the surfaces. Freezing rain is formed completely of liquid droplets, unlike sleet, ice pellets, or hail.
The freezing rain falls and solidifies on a wire fence as the rain is changing from a liquid to a solid state by withdrawing thermal energy, ultimately resulting in freezing.
When rain falls, the freezing rain droplets are in motion, that is kinetic energy. When they fall on a fence and remain stationary, they now possess potential energy. Potential energy means energy at rest while kinetic energy means energy in motion.
Also the freezing droplets of rain change from liquid state to solid state as they solidify on the wire fence.
