Yeah, everything works on energy. A lot of times it’s only hard to come by when you don’t properly manage it, though. So spamming Bladestorm a lot is gonna make you run out of energy faster.
However, there are a couple ways to get it back. Using gear items and some weapons/Warframes have energy regeneration as a bonus. Gear items are far more consistent, though.
Lot less scary once you’ve been playing for a little while. Guns are a huge asset in the game, and are quite powerful. Helps a lot when you’ve got a double-barrel sweeping through the baddies.