Field theory is important for the following reasons:
1. Field theory helps to understand the behaviour of particles when they are placed at different points in the field.
2. When any particular forces are applied on the particles, field theory helps to understand the magnitudes of these forces at different positions and when the same magnitude acts on the particles at different locations but at the same time.
3. Field theories such as electric and magnetic field theories can be used for studying the electric and magnetic field of a unit positive charge.
4. Electromagnetic waves can be studied with the help of field theory.