Are you talking about metal clips molded in a plastic body? Not hard to do at all. make sure the mold can seal off on the metal clip when you injection mold the plastic, so that there is no leakage of plastic over areas you don't want.
Or you can assemble pre-molded plastic bodies to the metal clip and ultrasonic weld together.
There are a lot of ways , depends on you design and customer's requirements, etc.