Sometimes parts end up being a combination of plastic and metal. It may be a simple thing such as a thread inserts in a plastic part or a screw thread for a handle, but more advanced solutions are also possible. In order to reduce assembly costs it is sometimes possible to cast a sheet metal flange into a plastic part for example, or to let a silicone rubber handle be cast
directly onto a metal surface. In some cases everything is done in a single process, in others the parts are made individually and assembled in a separate process. Volume and the willingness to invest in tools and processes decide what is best for your product.