This page is demonstrating the creation of metaballs in 2D and 3D using opengl


Metaballs rendered in 2D without the use of shaders can be found here


Metaballs rendered in 3D without the use of shaders can be found here


Here is an example of what you can do with 2D metaballs using just the glsl fragment shader.

Here is an example of rendering 3D metaballs using a naive ray marching technique.