Forum:"Priority" on the summoning of XYZ fusions

This topic would also apply for Chimeratach Fortress dragon and some other cards.

Perhaps the title is not very clear, so I'm going to explain:

Let's suppose I already have a X-Head_Cannon on the field and my opponent has a set trap hole, I normal summon a Y-Dragon Head, could I call for priority to summon a XY-Dragon_Cannon before my opponent could activate his trap hole?

Regards.