When does priority actually matter in magic? I have been playing Magic since Time Spiral and have never once seen the rules for priority matter. I've never heard a question from a player about a game situation to which the answer was, "Oh, well it's right here in the rules for priority."
Let me elaborate. Most other games handle questions of precedence (I want to do this but my opponent wants to do something conflicting) with a system of priority. Magic handles questions of this type with the stack. Here are some examples:
I have a 2/2 and I want to play Giant Growth on it while my opponent wants to kill it with Lightning Bolt? Resolved by the stack. Priority doesn't actually matter here. It's not a question of who has the option to act first, it's about who does act first, and because the person that acts first in this situation loses, the solution (given both players run Telepathy) is for both players to pass and the game to move on to the next step or phase. But this isn't a quirk of priority, this is that the Nash Equilibrium given perfect information and how the stack works is for neither player to cast his/her spell.
I want to cast Silence on my opponent during his/her upkeep but he/she wants to cast Lightning Bolt on me first. Sure, a player get's priority on his/her turn before other players, so he/she has the option to cast a spell before I can cast Silence, but it doesn't matter! Since this all happens during the upkeep, the spell I want to cast has to be instant speed anyways, so it can be cast in response to Silence while Silence is on the stack. Since Silence only takes effect on resolution, what order it and another spell are cast in won't change either spell's resolution (unless the other spell is a counterspell). In almost all situations, Silence only changes the ability for the player to cast things post-upkeep.
In all of the above situations, the stack is what determines what happens. Players priority in putting things on the stack doesn't matter since in the above cases (and the overwhelming majority of cases I've seen), as it is the ability to react that matters, not the ability to act first.
So, given how the stack works, does priority actually matter in Magic? If so, what types of situations do the rules for priority needed to actually determine what happens?
For reference, here are the rules for priority:
- 116.3. Which player has priority is determined by the following rules:
- 116.3a The active player receives priority at the beginning of most steps and phases, after any turn-based actions (such as drawing a card during the draw step; see rule 703) have been dealt with and abilities that trigger at the beginning of that phase or step have been put on the stack. No player receives priority during the untap step. Players usually don't get priority during the cleanup step (see rule 514.3).
- 116.3b The active player receives priority after a spell or ability (other than a mana ability) resolves.
- 116.3c If a player has priority when he or she casts a spell, activates an ability, or takes a special action, that player receives priority afterward.
- 116.3d If a player has priority and chooses not to take any actions, that player passes. If any mana is in that player's mana pool, he or she announces what mana is there. Then the next player in turn order receives priority.
- 116.4. If all players pass in succession (that is, if all players pass without taking any actions in between passing), the spell or ability on top of the stack resolves or, if the stack is empty, the phase or step ends.