Attaching a Face to a Body/head?

I modeled the entire body of my character. Then I modeled the face as a different object because I know there’s just about no way I can really make my complicated mesh’s head into a detailed face. I was working with quads early on, however I started doing loop cuts a bit too early, and later I also had times when I had to merge vertices, so almost the entire model is NOT composed of quads. This has made it difficult, so I have decided to model the extensions of the model (head, hands, and shoes) seperately and then merge them onto the body (somehow).

All I really want to know is how do I copy one object’s geometry and add it to the other; then I can start merge vertices and do other things like that. Mesh union is not working, it oddly removes a lot of geometry behind the face.

Join meshes by selecting them (hold shift for multiple selections) and Ctrl+J to join them into one object. You can then fill in the gap between them. To merge vertices use Alt+M

Thank you.