From “Geometry” PDF

Metaballs can be thought of as spherical force fields whose surface is an implicit function defned at any point where the density of the force field equals a certain threshold.

Is there a way to access that trashold value and implicit function?

hmmm….like maybe changing the function?…a noise metaball would be kinda cool…

Is there a way to access that treshold value and implicit function?

Not directly. You need the HDK (Houdini Development Kit) to do that.

As for the noise metaball field, that would be interesting but there is an alternative. i3d can interpret metaball fields and create noise saved in an i3d file. You could then sample in to the i3d field and drive stuff from that. Your own custom noise function embedded in an i3d file. You could use this to drive particle positions for example.