Here's a peacock (male) and a peahen (female). The peahen is the smaller, mostly brown bird next to the big rainbow colored peacock.
As has been pointed out, in many groups of animals, particularly birds and fish, the males are the flashy colorful ones that strut around (especially birds) and show off to the females.
It happens in a lot of mammalian species too. The
lion's mane, for example, is actually a physically costly thing out in the hot African environment. But it shows off his fitness and makes him look bigger. Some lions have
black manes, which are the least efficient because dark colors absorb a lot of energy and increase body temperature in hot environments. So the lions that do have dark manes, are fit enough to support and display such a drawback.
The silver back of a gorilla is also for display purposes to males and females regarding his dominance.
Similarly in some cultures such as ancient Greece, men were viewed as the beautiful gender. They're larger and have more muscle definition (and personally, I
love the musculature of a fit male torso). Beards apparently serve a similar purpose to manes, since they don't serve any huge physical purpose, can be used against the wearer in a fight by being an effective grip, but they make the wearer's jaw look larger and therefore make him look more dominant and stronger, and they only grow after the age of sexual maturity. Female breasts don't have to be as large as they are for milk production- large breasts don't generally produce more milk than small/medium ones, because the extra tissue is fat rather than extra internal structure for milk production. But, they are thought to serve as an indicator of sexual maturity, since young girls do not have breasts but physically sexually mature teens and adult women generally do.
Many men work out their chest and arms on a regular basis, requiring a lot of maintenance to maintain, to be larger even if they don't need that additional strength for a sport, and even though it's not really a contributor to health beyond basic fitness and exercise. It's often considered aesthetically attractive, though. All else being equal, many men would prefer to be able to take their shirt off at the beach or a pool or something and have a well-defined chest and stomach and arms, rather than ones that they're less than thrilled about visually.
So across multiple types of animals, including humans, both genders can potentially show off visually, with the more common one in many species generally being the male as far as I know.
In humans though, all of the focus about this gets put on women. Men can wear flashy clothes, can sport nice beards, can have an unnecessarily fast car or unnecessarily large truck, can in many cultures be bare-chested and show off his worked-out body, can walk with a noticeable swagger, but then when a woman wears heels or a dress, or shows long healthy hair, or shows off some cleavage, or just walks out in a tank top or without being covered from head to toe, there's this idea that it's mostly women that want to look sexy.