And this positive charge can be used to interact with different types of molecules found inside the active side. And so the positive charges on metal ions, as we'll see in more detail in the future lectures, they can be used to basically stabilize the transit transition states as well as the intermediate molecules that are formed within that active side. They can also be used to assist in actually forming a strong nucleophile. For instance, one will discuss carbonic and hydrates. We'll see that in carbonic and hydrates, inside the active side, we have a zinc metal atom that is used to actually form a strong nucleophile, the hydroxide nucleophile. And finally, this metal atom can actually be used to hold that substrate molecule in place.