Star Trek III: The Search for Spock (1984)

Watch this one only after The Wrath of Khan: it picks up shortly after that film and depends on how it ends. Leonard Nimoy's first film as director is a smaller, more personal story about how much the crew will risk for a friend, defying Starfleet's orders to do it. Christopher Lloyd plays Kruge, the Klingon commander hunting the secrets of the Genesis device, and it is the middle chapter of a loose trilogy that ends with The Voyage Home. That makes it worth a look before the whale film, even if on its own it is the most dependent on what came before.