After cameras and lenses, the third slice of your wedding gear triad is your choice of lighting gear. The most basic system revolves around a dedicated TTL (through the lens) flashgun mounted on your camera’s hot shoe (or preferably on an adjustable flash bracket).
With the right tools, outdoor wedding photography can be a nice contrast to the more formal, controlled-light look of photographs taken within the confines of a catering hall or other wedding-centric indoor location.
When it comes to studio flash systems, photographers face few limitations as per what’s possible. If you can sketch the shot on paper, you can shoot it. Power-wise, there are a number of power packs capable of banging out up to 6400 w/s symmetrically or asymmetrically into single or multiple heads.