Most materials don’t conduct electricity well. Rubber, plastic, wood, water (mostly), and air all do a poor job. Metals are different. They conduct electricity easily - which is why every wire in your home is metal. There’s a specific reason why.
In most materials, electrons stay tightly bound to specific atoms. To move them around, you have to put in a lot of energy. Metals are weirdly arranged. Their atoms are packed in a crystal lattice, and the outermost electrons aren’t really attached to any single atom anymore. Physicists describe them as a “sea of electrons” floating freely throughout the whole metal.
When you apply a voltage across a metal - connect a battery to it - those free electrons start drifting in one direction. That drift is the electric current. The lattice atoms barely move, but billions of electrons can slowly flow through. The best conductor is silver, but it’s expensive. Copper is nearly as good and much cheaper, which is why most household wiring is copper. Gold is also an excellent conductor and doesn’t corrode, which is why it’s used in connectors that need to stay reliable for decades.
