Metal Angel takes the idea behind a classic scrolling shooter game and adds some iPhone specific elements to it. Namely the control scheme is based completely around the iPhone's accelerometer. While this does make things interesting and mildly unique, it can also be a huge headache.
The game is very straight forward with no discernable storyline. You can pick from one of three ships and their different pilots before you start blasting away at your enemies. For the most part your enemies all look the same. Some of them are different colored ships that perform different attacks. There are a few that will surprise you however.
You are constantly firing in this game. All you really need to do is tilt side to side or front and back to move around. When you kill your enemies you'll notice that they drop gems and power-ups. Have fun trying to get to them as you're basically going to have to risk sliding directly into your opponents as the accelerometer control feels like you're ship is a marble.
If you enjoy scrolling shooter games, you'll enjoy Metal Angel. It takes a long time to get a grasp on the controls, but as you're not aiming for anything but a high score it won't be too depressing when you die. If you prefer your games to have other control modes besides accelerometer, then you should probably skip this game.