There are two forces at play:
- The gravitational force acting downward due to the mass of the bucket and the water that it contains.
- The upward force that your hand exerts on the bucket.
If the magnitude of the force your hand exerts on the bucket equals the magnitude of the gravitational force, the bucket is in static equilibrium. That means the bucket is not moving and the forces acting on it balance each other out, making the net force 0.
Having 0 net force means the bucket doesn't undergo any acceleration, or change in motion.