After breaking box office, critical, and audience expectations back in 2014 with “Guardians of the Galaxy,” James Gunn’s lovable team of misfits return to the big screen in a manner unfamiliar to most sequels. Movies aren’t about being better or establishing quality in relationships to other presentations. They’re about ideas and how best to execute them. In that regard, if “Guardians of the Galaxy” is about finding a family, “Volume 2” is about what it means to be part of one.

Being part of a family is big and messy. They butt heads, they’ll yell, they won’t listen to each other. And at the end of the day, they need each other more than anyone else. Lord, do these character argue.

The opening credits, a digitally constructed long-take sequence, reminds you of the gleeful possibilities of summer entertainment. It’s exciting and propulsive but hilarious and informative, showcasing how the Guardians have grown to work as a team in their time together. You’d be hard pressed to find a more entertaining opening to a Marvel Studios movie to date. It’s a sufficient appetizer to events about to transpire but the meat and potatoes are the character relationships.

Picking up several months after the Guardians saved the galaxy, the menagerie of miscreants are doing odd jobs. Their intent is still to go around helping people across the galaxy, but that doesn’t mean they can’t pick up a nice paycheck every now and then. Through a comedy of errors thanks to Rocket (who is still the universe’s most triggerhappy raccoon), the Guardians once again find themselves on the run from a seemingly endless army of people who want them dead. But what’s new?

The main narrative thread is kicked off after Star-Lord (Chris Pratt, charismatic as ever in the role that sprung him to stardom) and the Guardians are saved by his father Ego (Kurt Russell radiating in the confident swagger he’s known for). It’s a grand cliche to post a late film reveal about familial ties but what makes a series of films like “Guardians” so different is in how it revels in cliche, and expands upon what makes them entertaining to reveal a sincere emotional truth about itself.

Following in the footsteps of great sequels like “Empire Strikes Back,” “Volume 2” decides to narrow its focus on characters while losing constraints of a traditional plot structure. Developments in the story are entirely predicated on characters acting emotionally. It’s easily the most emotionally driven Marvel Studios film, and has more in common with great superhero epics like “Hellboy II: The Golden Army” and “Spider-Man 2” than other films in the studios lineup.

The Guardians split off into separate groups for the majority of the film. We understand how these characters bounce off one another but Gunn’s script sees it best to pair off characters in unexpected ways. The Guardians have to look at one another and, through better and worse, realize for themselves whether or not they even need a family in the first place.

It’s a movie that dives deeper into itself to share emotional honesty with a bumping soundtrack. In a nutshell, the music feels more suitable for what is occurring onscreen instead of the instantly iconic needledrops of the first film. That might be true of the whole film. While not composing new pop culture iconography in the same manner of the first outing, “Volume 2” gets introspective.

Actions have consequences, emotions are bombastic and a talking baby tree is endlessly adorable. Oddly enough, Baby Groot might be the least compelling character in the whole film. This isn’t a sleight against the character or his adorable factor, but rather a testament to James Gunn’s writing and direction for the rest of the cast. Not every character gets as large an arc as Star-Lord but all of them feel emotionally huge.

Gamora and Nebula, sisters and hardened survivors of the space warlord Thanos, once again are at odds with one another but in confronting one another also confront their troubled history and have to decide whether or not to let it define them. Drax finds common ground with newcomer Mantis, an empathetic alien who can understand emotions, though finds herself at odds with common sense. Rocket gets to bounce off Yondu and the two bond over their anger while forging an unlikely partnership. It’s Yondu who gets the most surprising amount of focus.

As Yondu, Michael Rooker delivers his finest performance to date and juxtaposes his emotional journey against Star-Lord’s exciting new relationship with Ego.

Ego is also a sentient planet, by the way. Ego’s Kurt Russell form is a construct of flesh willed into existence by the sentient planet who has traveled across the stars seeking life and purpose.

There are still hints of that bigger Marvel universe establishment happening in the background. Space battles galore and extended sketch comedy bits that would feel at home in a galactic “Saturday Night Live” are welcoming, but “Volume 2’s” own essential purpose is in exploring who these characters are and what they mean to one another. That a standalone sequel can manage this sense of identity is impressive. That this is the fifteenth entry in a shared universe is astounding and proof that the Marvel machine won’t run out of gas anytime soon.