In Wonder Woman, soon after Princess Diana of Themyscira (Gal Gadot) and Captain Steve Trevor (Chris Pine) arrive in London, they are ambushed in an alley by a gang of German spies. Moments later, one of the Germans opens fire on them and - to the shock of every man in that alley - Diana blocked the bullet with her Amazon gauntlet. She does it several more times before Diana and Trevor overpower their would-be assailants. Later, at the "No Man's Land" of the Belgian front lines of World War I, Diana sheds her disguise and confronts the German army in her full Wonder Woman regalia. The German soldiers shoot at her and she repeatedly blocks their bullets with her gauntlets.
This is Wonder Woman's signature move. It has always been undeniably cool. Like Spider-Man swinging across New York City on thin strands of webbing, Batman frightening criminals with his silhouette, or Superman tearing open his button-down shirt to reveal the S-shield underneath, blocking bullets with her gauntlets is something indelibly associated with Wonder Woman. However, in director Patty Jenkins' Wonder Woman, as the powers and godly status of the Amazon Princess have now been established within the DC Extended Universe and going forward, as awesome as it is when Wonder Woman blocks a bullet, one has to wonder - Does she even need to do this at all?
Is Wonder Woman bulletproof? Why wouldn't she be? She is a god. By the conclusion of Wonder Woman, when Diana confronts Ares and "levels up," she fully comes into her powers after Ares revealed she is not only the daughter of Zeus but the sister and equal (even superior) of Ares - the true god-killer born to kill the most malevolent and last of the pantheon of Greek gods. Wonder Woman has risen beyond the Amazon she has always believed herself to be. One of Diana's journeys in the movie is an evolving understanding of her physical abilities. Her Amazon training taught her how to be a warrior, but because her mother Queen Hippolyta (Connie Nielsen) wanted to protect her from her true heritage, she was kept in the dark about how much power she wields and how much more she was actually capable of.
For her whole life up to her involvement in World War I Diana believed herself to be no better than her Amazon sisters when in actuality, she was always so much more. She doesn't share their vulnerabilities - such as how they can be killed by bullets - which she learned first hand when German soldiers stormed the beach of Themyscira and engaged the Amazons in battle. Bullets cut down and killed several Amazons, including Diana's aunt and mentor Antiope (Robin Wright). Naturally, she feared the bullets that came from the weapons of man, and when she learned her Amazon gauntlets can block those bullets and keep her safe, she, of course, relied on this newfound ability. But now, with her understanding of herself as a full-fledged god (or even as a demigoddess being half Amazon), does she need to ever fear bullets?
Granted, in the course of 75 years of comic book stories, Wonder Woman wasn't always a goddess in the literal sense. This divine nature to her origin where she is now the daughter of Zeus as opposed to a being molded from clay and given life by the gods (her original origin, as told to her as a fable by Hippolyta in the movie), is a relatively recent upgrade to her powers and status. As DC Comics' greatest female superhero, it places Wonder Woman on more equal footing with Superman in terms of power levels.
For most of her comic book existence, Wonder Woman was merely much stronger, faster, and more durable than an ordinary human. Yet she was susceptible to being mortally wounded by any number of means. (The Amazons in the movie are generally portrayed in this way - they are amazingly long-lived and do not age, but they are mortal in the sense that they can be killed). Of course, Wonder Woman's powers always fluctuate in accordance to the whims of whoever is writing her comic books and by the editorial mandates of DC Comics. Yet blocking bullets with her bracelets has remained something Wonder Woman always does.
It was Lynda Carter's legendary portrayal of Wonder Woman in the classic 1970's television show that popularized blocking bullets with her bracers. That move, along with her spinning in place as Diana Prince to magically transform into Wonder Woman, left a lasting and defining impression on generations of fans. The television Wonder Woman was the character from the comic books of that era come to life - an Amazon magically stronger and longer-lived than a normal human, but not immortal, and not possessed of the power levels of a god. Carter's Wonder Woman definitely needed to block bullets with her bracelets, and it never stopped being cool.
Gal Gadot's cinematic Wonder Woman continues this legacy, in part because it's expected as a defining trait of the Amazon Princess, but also because it's crowd-pleasingly cool. And yet, the question remains if she even needs to do this at all anymore - or did she ever? Even before her climactic battle with Ares, Wonder Woman smashed through buildings made of brick and wood with relative ease. She was clearly durable enough to withstand all manner of blunt force trauma with no ill-effects. By the time she fought Ares, she was absorbing the worst punishment she'd ever endured up to that point. Ares was slamming her into the asphalt ground of an airfield and driving sheets of metal at her. If Wonder Woman can take all of that damage without injury, why would a bullet be able to penetrate her skin?
One thing to keep in mind, however, is that from a filmmaking point of view, it's important to find ways to differentiate superhero characters, especially when they meet and fight side by side, as Superman and Wonder Woman have (and will again). Superman is absolutely bulletproof; since his earliest days as a character "nothing less than a bursting shell can penetrate his skin." For decades, Superman has been proudly invulnerable to gunfire - every part of him, as Brandon Routh's Man of Steel proved when he let a criminal shoot him point blank in the eye and let the bullet bounce off his eyeball in Superman Returns.
It's hard to imagine Superman using a shield to protect himself from machine gun fire. Just as Wonder Woman can apparently fly, to contrast her with Superman, she won't soar at enemies the way he does, and she will never stand still, puff out her chest, and let anyone open a barrage of gunfire at her, where Superman just calmly lets the shells bounce off his S shield. That's Superman's thing. Wonder Woman, who is by far the superior hand-to-hand combatant, fights and defends herself as only Wonder Woman can.
Though it makes little sense, considering that she has the powers of a Greek god, that Wonder Woman isn't bulletproof as part of her wide range of invulnerability (such as walking through a town covered with deadly mustard gas with absolutely no ill-effects), we likely will always see her using her gauntlets to block bullets. Even if she doesn't actually need to. That move - which will forever be imitated by anyone fantasizing themselves to be Wonder Woman - is one of the primary things the greatest female superhero icon in the world is known for. It's a move anyone wishes they could do; after all, none of us are gods. Like her magic lasso and her tiara, Wonder Woman simply wouldn't be Wonder Woman without blocking bullets with her gauntlets - even if she never truly has to fear speeding bullets.