appearance

Vampires in the Twilight universe possess several similar physical traits. The change into a vampire gives the person very pale, white skin, and marble features. The angles of a person’s face are perfectly aligned, and what physical features were already there before their transformation are enhanced, to make the vampire the ultimate predator—these enhanced features entice their victims to come near them, making them vulnerable to attack.
Also, a vampire’s teeth are very sharp—as they are their weapons for hunting. The vampires do not have fangs.
When changed into a vampire, a person remains the appearance, height, and weight that they were before the transformation, except that the physical features of the person will be enhanced. Natural changes in the human body would no longer occur. All growth in the body; your body remains “frozen” in the state that you were changed. You will no longer gain or loose any weight. Your hair, fingernails, and toenails don’t grow, and your heart stops beating. All of your bodily systems no longer function. But, vampires in the Twilight universe do have one deadly weapon:  they can produce venom. When bitten by a vampire, their venom will travel through your bloodstream through your veins, and make its way to your heart, slowly changing you into a vampire over the course of roughly three days. Once the vampire’s venom reaches the heart, the transformation into a vampire is completed. The venom can also somewhat substitute for saliva, keeping the mouth wet, although vampires do not produce saliva.
Because a vampire’s bodily systems no longer function, they do not have blood circulating through their body; this is the reason that they are so pale. They don’t give off heat either; in fact, their skin is nearly ice cold. Their skin is also very hard, and it cannot be broken or torn by anything except the teeth of another vampire, or a werewolf. Also, vampires aren’t affected by disease or sickness.
Most civilized vampires have several qualities that make them the ultimate predators. First of all, their physical appearance is inhumanly beautiful. Their aloofness is compelling, and their physical grace is “dazzling” to human eyes. Their scent and voice draw in their prey, and their smile reveals their white and perfect teeth.  
Vampires are also gifted with great strength and speed, and are nearly indestructible; there are very few ways vampires can be killed: either by other vampires, or by werewolves. Mostly, vampires die by being torn apart into pieces, and then the pieces and burned.
Skin tones of a vampire may vary, because of the previous nationalities of the vampires, but even a person who had a darker skin tone while human while obtain pale features, although their skin will seem somewhat like an olive colour, or darker. 
Vampires are unable to sleep, so naturally, they have dark or purple circles under their eyes from sleep deprivation—although they don’t get tired. This means they have a lot more time on their hands. 
Vampires don’t need to breathe either. But, most do as a habit, because in order for them to use their sense of smell, they have to breathe. It is not necessary, but vampires are capable of breathing, although it is not because of a need for oxygen.     The appearances of vampires in the Twilight universe can vary, depending on a couple of variables. The first, being how physically attractive the vampire was before they were changed.  The change into a vampire enhances what was already physically there in a person when they were human. Vampires can seem more or less physically attractive depending on how they appeared while they were humans.  
The second variable is whether a vampire feeds on animal or human blood. If a vampire feeds on animal blood, its eyes will change colour very frequently, depending on how thirsty it is, and when it last fed. These “vegetarian” vampires have dark golden coloured eyes, but after the vampire feeds, their eyes turn lighter, to a soft gold or topaz. As they become thirstier, their eye colour will darken. It takes about two weeks without feeding for a vampire’s eyes to become entirely black. If a vampire feeds on human blood, its eyes turn a deep burgundy colour. The vampires that feed on human blood are considered to be uncivilized. Newborn vampires have vivid, bright red irises because of the large amount of human blood left over in their tissues from before their transformation into a vampire. The red colour fades gradually over a year’s time.
The “vegetarian” vampires move in a way that is described as fluent and fluid; their movements are very graceful. But, the uncivilized vampires which feed on human blood move in a feline or cat-like manner—their posture is a crouched position. They are seen as wild and uncontrolled creatures. Newborn vampires behave in a similar manner. They are very wild and although they have superior strength, they have minimal skill. They are sadistic and wild with a thirst for blood for about a year, until the uncontrolled behaviour begins to wane.