Newton's Law of Universal Gravitation states that the force of gravity between two objects is directly proportional to the product of their masses. This means:

* If the mass of one object increases, the force of gravity increases.

* If the mass of both objects increases, the force of gravity increases even more.

Here's the formula:

F = G * (m1 * m2) / r^2

Where:

* F is the force of gravity

* G is the gravitational constant (a constant value)

* m1 and m2 are the masses of the two objects

* r is the distance between the centers of the two objects

So, the greater the mass of the objects, the stronger the gravitational force between them.