The deltoids wrap around your shoulder, which means that it’s impossible to build them from front-to-back with any one exercise. And while many exercises hit the anterior (front) and posterior (rear) delts, it’s the medial or middle delts that often get left out.
The act of loading the shoulder while it moves out to the side of the body is necessary for activating the middle deltoid. The middle delt displays its strongest force-producing potential between 60 and 120 degrees of shoulder abduction. So, to torch this head of the muscle, use the lateral raise and make the mid-range of the movement the hardest part. A popular technique here with dumbbell lateral raises is using a little body English to gain momentum to overload the peak contraction.
Here’s another way. Use resistance bands. That may sound weenie, but studies have shown bands work just as well as dumbbells for this exercise, maybe better. Performing the lateral raise with a band stresses the muscle more in the mid-range, where it’s most active.
It also means you can spend more time pushing against the peak contraction with the greatest load rather than being pulled back through the eccentric (lowering) portion with a dumbbell.