The first time I saw usual suspect at the opening seen I thought that it was the real story but just putting the last seen at first. It was exciting seeing the seen because of its suspense and the entire big explosion. But only the second time that a saw it I realized that it was giving us a easy clue that the real enemy was always among us because of the part where you see after the explosion when the camera is zooming on a wall of ropes with a little hole in the middle, which tells us that something, is in there.
I think that the scene that is shown at the beginning is to tell us about the tone of the movie, what kind of movie it's going to be.
Is it going to be a comedy or action etc? In order to show you what kind of movie it's going to be they use very hard lightening.
Close ups of the enemy character without revealing his face. And the way they set up the scene no light except for the light coming out because of the fire, which shows that there is going to be violence and action and killing and so on.
The sound is also a sign of action and confusion because of its little opera tone where it goes from a little sound and back to a big sound and so on so that it confuses us. And the slow cutting and camera movements gives us another clue that the master mind in this story acts very slow but very sneaky and bright. In one of the beginning scenes you see a close up of a lighter which indicates that something bad is going to happen, something is going to explode. There are many of those small details in the movie at the opening scenes they make you understand and predict easily what's going to happen at the end.