The movie's biggest message is about the importance of team building and working with others for the greater good. Each of the superheroes alone couldn't defeat the enemy, but together, they're much stronger. Also shows how a team's (or neighborhood's or society's) different strengths and abilities are what make it powerful.
Lots of large-scale superhero-movie violence: huge explosions, widespread destruction, battle sequences. There's no gore (with the exception of the parademons' gooey green blood), but a giant monster tosses even the superheroes around like they weigh nothing, kills foes, and destroys buildings. A resurrected Superman angrily fights with and injures Batman. A family is armed but can't fight the parademons; they nearly die but are saved at the final moment. Tons of weapons (swords, guns, hammer, trident, lasso, shields, etc.) and hand-to-hand fighting.
Shirtless shots of various male characters; a couple of scenes of a reunited couple kissing and embracing. Mentions of Wonder Woman's beauty/attractiveness.
A few uses of strong language, including "s--t," "s--thole," "a--hole," "hell, "damn," "Jesus," and "son of a bitch." A couple bleeped uses of "f--k."
Several shots of expensive Mercedes cars; lots of tie-in merchandise, including apparel, games, figurines, etc.
Drinking, Drugs & Smoking
Adults drink in pubs and alone. Aquaman downs a bottle of liquor and then throws it into the sea. Bruce and Diana have a drink together.