On one hand, it would obviously attract lightning, being a tall-ish conducter it would attract it, but cars and the like are said to be (relatively) safe specifically because they direct lightning around you to the ground. I imagine it would be similar to that.
If the metal gazebo is grounded, and you are not, you’ll be protected if lightning strikes the gazebo because electricity will always follow the path of least resistance to ground.
Have you ever seen one of those videos of a guy in a metal suit playing with the lightning from a Tesla coil? Same principle.