Simply stated, most metals are good electrical conductors, most nonmetals are not. Metals are also generally good heat conductors while nonmetals are not.
VOLTAGE: This is the pressure the water is under. We can also think of this as the force that we push or pull something with. Effort is another word we can use here.
In this example, the force the person uses, which is the voltage, affects the speed at which the car will move (the current). If you've ever had to push a car, you will know how this works! The harder you push, the faster it goes. From this we can see that as Voltage increases, Current increases. That means that the harder you push the electricity through the circuit, the faster it goes and the more of it you can move at any one time.
Let's put that into physics-speak: as Voltage increases, Current increases.
RESISTANCE: This can be seen as blockages in the water pipe. It can also be seen as friction which acts to slow down a moving object
Another take on the above example is that of pushing a light car compared to pushing a bus. The heavier car takes a heck of a lot more effort to move than the light one. Have a look: The weight of the cars is like resistance in electric circuits; it makes it harder to move. The more weight, the more pressure you need to make the car move....