In what ways does dark matter help in "binding" celestial bodies together in a Galaxy?

Earlier in history, it was said that the celestial bodies in galaxies were bound by "mutual gravity". There is still a common misconception that the gravity of supermassive black holes binds things in the gravity, similar to how planets revolve around their parent star, which of course is not true, because studies say dark matter plays an important "role" in stabilizing a galaxy at the same time supermassive black holes also plays an important role in galaxy formation.

Question: How does dark matter actually bind things in a galaxy together? What role do supermassive black holes play other than controlling the star formation in the galaxy?

• An example: in the Milky Way, there is about $5 \times 10^{10}$ solar masses in the form of stars, about 10% as much in the form of gas, and about 10 times as much in the form of dark matter. The central supermassive black holes has a mass of only $4 \times 10^{6}$ solar masses, about one ten-thousandth of the total stellar mass and one one-hundred-thousandth of the total mass. So the SMBH has no effect on binding the galaxy together (except in the innermost few light years). Feb 22 at 12:44