Surface tension can be described as "the tendency of liquids to minimize their surface area." The molecules closer to the surface of a liquid has higher potential energy. This means that the molecules deeper than the ones close to the surface, has to gain energy in order to move upwards to reach the surface. Since the molecules want to have lower energies to be more stable, they want to stay closer to each other by making the surface area smaller. The decrease in intermolecular forces causes surface tension to decrease too.
Everybody must have observed that water droplets are spherical. The larger the droplets become, they are more effected by the gravity and lose their shapes.
Check it out what happens at zero gravity :