Using Metaball Force
Create some metaballs using the Metaball shelf tool.
Click the Metaball Force tool on the Particles tab.
Select the metaballs you want to affect your particles and press Enter.
You can set the Force Scale parameter on the Metaball Force node to either attract or repel particles. A positive value will attract particles and a negative value will repel particles.
By default, this tool applies a Radial Force, which can be changed to Directional Force on the Force SOP. There are also force controls for axial, vortex, and spiral forces.
The following example shows the metaballs repelling the particles.
For specific parameter help, see the Metaball Force node help.