If the guardian is a deliberate fighter, then the warrior is more of a berzerker, concerned more with attacking and killing as quickly as possible than defending against enemy attacks. Warriors are capable of using the widest variety of weapons of any profession, ensuring that you'll always have plenty of options available to you if you want to vary things up as you level.
In addition to straightforward hacking and slashing, though, the warrior brings a few unique skills to combat. The most notable of these when grouped with a warrior are the banners that they can summon: a warrior will plant a combat banner into the ground, giving buffs to all nearby allies. These banners can be picked up and moved around if the battle migrates to another area, and can even function as weapons themselves. There are a few different types of banners, ranging from the defensive-minded Banner of Defense to the more offensive Banner of Strength.
Use your adrenaline to deliver powerful attacks; just try not to get blown up while doing so.
Warriors use their rage to fuel them in battle, and landing blows and taking damage will fill an adrenaline meter located above your skill bar. You'll start with just a single adrenaline bar, but you'll quickly unlock a total of three. When your adrenaline bar fills, you can use the F1 key to unload a powerful attack, called a Burst, on your enemy. The type of attack you use is dependent on your weapon; a rifle may pop out a single, extremely powerful attack, while a sword/sword combo might let you slash repeatedly and quickly. Experiment with different weapon combinations to find something you like, but keep in mind that your adrenaline will fade over time once you exit combat.
When the warrior chooses to buff their Burst Damage via traits, that will, predictably enough, cause their burst skills to deal more damage. Simple!