Combat is the main gameplay aspect of Guild Wars 2. Almost all the PvE quests in the world of Guild Wars involve fighting. This is even more so the case in the PvP and WvW game modes that are solely about the combat experience itself. Guild Wars 2 does not follow the "holy trinity" design found in other MMOs, where professions fall into tank, damage, and healing. Due to a diverse skill system allowing for a multitude of vastly different character builds, every profession in Guild Wars 2 is capable of fitting each of the combat roles (damage, support, control) or are sometimes even the result of a combination of them.
Every profession has the tools to survive on its own. As a result, there even is a skill slot in the skill bar reserved for a healing skill, and every character has the ability to dodge attacks. Despite being able to play most of the game solo, there are occasional events that require more than one player, such as dungeons and champion level bosses.
 Combat basics
 Combat mode
Players can easily tell if they are in combat by the way their skill bar appears; while in combat, the skill bar is surrounded by yellow haze. Combat mode is normally triggered by attacking or being attacked by an enemy, being damaged in any way or receiving hostile effects like conditions. While in combat, the character's health won't recover naturally, while out of combat the health regeneration is very rapid. Some actions like reviving take longer in combat than while out of combat, and some actions like use of waypoints is not permitted while in combat.
 Actions not permitted in combat mode
- Waypoint travel
- Entering WvW (however, you can enter WvW if you queued before entering combat and get enter WvW dialog)
- Changing traits
- Changing skills
- Unequiping items (including gathering tools)
 Skillsskill bar always plays a central role in combat. It can carry a maximum of ten different skills, most of which are initially locked, and looks different based on profession, chosen skills, and equipped weapons. Skills can be used to damage and debilitate opponents and aid the user and their allies to attempt to win the battle.
The slots in the skill bar are reserved as follows (cf. picture):
- Slot 1-5: weapon skills
- Slot 6: healing skill
- Slot 7-9: utility skills
- Slot 0: elite skill
- F1-4: profession mechanic
In addition to the explicit effects of skills, any character damaged by an opponent is placed in "combat mode", which reduces their forward movement speed, increases the cooldown on swapping weapon sets, and prevents the character from changing his equipped items or skills. Combat mode ends after a certain length of time without taking damage.
Certain conditions, such as poison, can sometimes continue to inflict damage and keep a character in combat mode for a significant time even after all opponents are defeated. On the other hand, a character that avoids damage (for example by dodging or using aegis) can sometimes stay out of "combat mode" even while under direct attack.
 Swapping weapon sets during combat
Swapping weapons is one of the key combat elements in Guild Wars 2.
Most professions can have a second weapon set readied. That allows players to switch back and forth between weapon sets, which will instantaneously replace the first five slots of the skill bar (the weapon skills) based on the weapon set the player is currently wielding. A player is thereby effectively replacing his or her five core skills.
Weapon-switching is especially useful
- to extend the number of skills available in combat,
- to avoid long cooldowns on skills,
- to make use of the different weapon properties (such as range) in combat.
Note: Both the elementalist and engineer profession can only ready a maximum of one weapon set at a time. However, elementalists may achieve similar effects by switching attunement, whereas engineers can equip various weapon kits or device kits.
 Avoiding enemy attacks
Every character has the ability to dodge incoming attacks at the expense of endurance.
The best time to initiate a dodge is when the enemy is executing a powerful attack. This is much easier to do in PvE because the monster types that you encounter in the game have, for the most part, a somewhat clear indicator of when they are going to unleash a powerful attack. This can be, for instance, an exaggerated attack animation or simply the glaring of the enemy's eyes.
There is no basic attack in Guild Wars 2, for all attacks require the player to activate a skill in the skill bar.
However, any skill slot can be put on auto-attack. It is thus possible to activate a skill as soon as it is recharged if no other skill is currently being cast. By default skill slot 1 of each weapon set is set to auto-attack.
Note: Most environmental weapons do not have a default auto-attack.
 Chain skills
Some skills create chains with others. Upon successful activation of a chain skill, it is replaced by the next in the series. Chains are reset if another skill outside the chain is used, if the player is interrupted, or when the chain completes.
Certain skills can dynamically combine their effects in a combo that produces an extra benefit beyond the skills' normal effects. Skills that can begin a combo create "combo fields", and skills that can complete a combo are called "combo finishers". Both skills do not necessarily need to be performed by the same character, and in fact many combos are only possible using skills from two different professions.
- In the game window, the color of the level of the mob varies depending on the character's apparent (or adjusted) level viewing it. If the character's level is four levels or more higher than the mob, the mob's level has a greenish tint to it. If the character's level is 3 or more levels below that of the mob, the mob's level has a reddish tint to it. If there is even more of a level difference, the mob's level appears in a reddish-purple color.
- According to The Making of Guild Wars 2, at one point during development, the combat system of the game literally consisted of aiming and shooting, similar to action game genre.