How to summon
Summons have been handled in different ways throughout the Final Fantasy franchise over the years, with the way it's used in Final Fantasy VII Remake being a bit confusing about how to trigger it. This is because there is actually no guaranteed way to send summons, so don't expect to bring them out in every fight to crush the enemy you're up against.
Instead, summons are saved for matches which are a bit more difficult and last longer than 30 seconds. If you are in any of these longer fights, especially a boss fight, you will notice that a summon gauge appears on the right side of the screen above your party's HP info and the like. .
Once this gauge is full after a short time, you can bring and Summons that your party members have equipped to their Materia Summon slot. However, you will need at least half of your ATB bar full to produce a few Summons, while a few others require a full bar to do so.
Once the summon is complete, it will help you fight alongside you for a period similar to the reverse of the original summon gauge. The character who killed them will unleash an ultimate attack and leave however.
While the summon is on the battlefield, you can use one of the two summon abilities by selecting them from the command menu. You're not just limited to using them with the character who received the summon, as anyone with a half bar or full ATB can choose selected abilities for them that depend on how well you have the spell. ATB bar. If whoever used the summon remains alive, the timer will eventually activate and the summon will use its ultimate attack before leaving the battlefield, dealing major damage to the enemy.