Metaballs, also known as blobby objects, are a type of implicit modeling technique. We can think of a metaball as a partical surrounded by a density field, where the density attributed to the particle (its influence) decreases with distance from the particle location. A surface is implied by taking an isosurface through this density field - the higher the isosurface value, the nearer it will be to the particle.

An Overview of Metaballs/Blobby Objects