You are given a hammer, a battery, a bulb, wires and a switch.
If the substance can be hammered to convert into sheets then it is metal if it is broken into pieces then it is non-metal. Set up the arrangement using bulb, battery, wire and switch as shown in figure. Place the substance between Point A and B if the bulb starts glowing then the substance is a Metal otherwise it is non-metal because metals are good conductor of electricity.
Generally above methods can be used to identify metals and non-metals. But there are some exceptions also for example Sodium is metal which is not malleable in fact it is brittle. Graphite allotrope of non-metal carbon is a good conductor of electricity.