Why do we need a resistor in a cicuit? What will happen if there is no resistor?

Actually the resistance is the characterstic of a conducting material. In metals( conducting material) there are free electrons and when we connect battery , they accelerate  towards the positive terminal. But there are heavy atoms which are bound with each other. The electrons collide with these atoms andthese atoms provide resistance in the way of electrons.

 

If resistance is zero the current will be infinite.