Common Sense Note
Parents need to know that The Avengers is a superhero adventure in which many of Marvel's major characters -- including Iron Man (Robert Downey Jr.), Captain America (Chris Evans), Thor (Chris Hemsworth), and Black Widow (Scarlett Johansson) -- come together to battle an otherworldly enemy in a war to the end. From the first scene on, there's virtually nonstop comic book mayhem, including advanced weapons, epic-scale battle scenes, and thousands of casualties. Some of the fights are deeply personal as relatives face off, and some people do die, including characters the audience will care about. The heroes sometimes discuss their motivations for fighting crime, and the discussions can be intense, though it also leads to a good deal of camaraderie and cooperation. Expect some swearing ("ass," "son of a bitch," etc.), plenty of snarky quips from Iron Man, an off-hand joke about adoption that could upset some families, and intense 3-D action.
Sexual
Content
Some flirty banter and form-fitting outfits. Bruce Banner is briefly shown naked, but no sensitive body parts are shown, and it's not sexual in any way.
Violence
Hugely explosive, destructive mayhem throughout most of the movie. There's not much in the way of gore/blood, but cars are flung from overpasses, a giant monster tosses people around like rag dolls, entire armies are decimated by lasers, massive explosions and mega aliens destroy buildings, etc. Casualties aren't lingered on, but they're presumably in the thousands; use of nuclear weapons is discussed. In one startling scene, an important supporting character is killed; other characters are injured. Lots of weapons (guns, hammers, shields, arrows, hands, bombs, and more) and fighting. The bad-guy aliens are pretty creepy looking.
Language
A few uses of words including "ass," "hell, "damn," "bastard," "oh my God," and "son of a bitch."
Social
Behavior
It's clear: Teamwork matters. The Avengers are best when they're working toward the same goal instead of letting others tear them apart. And the movie makes it very clear that you can step up and be a hero no matter what mistakes you might have made in the past. That said, not everyone in the "good guys" camp is always entirely on the up and up, and the heroes do have their share of conflicts before they come together. And violence is the primary means of conflict resolution (with tons of collateral damage).
Consumerism
Tie-in to vast quantities of related merchandise. Signage for Acura, Citibank, and other brands can be seen.
Drugs / Tobacco /
Alcohol
Some champagne toasts. One character mixes a drink for himself. A very brief reference to "weed."