Almost Perfect Old-School Gem
You start Metal Storm because you hear that it has a quirky gravity trick - you finish Metal Storm because of the well thought out and creative level design. So here's how Metal Storm works - its your basic NES side-scrolling shooter where you roll your character from Point A to Point B and fight a boss at the end of each level, but here's the catch - at any point in the game you can reverse gravity.
Reversing gravity is a cool gameplay concept that was certainly ahead of its time, it adds a new level of complexity to the combat although it really shines through Metal Storm's platforming, which is closer to puzzle solving in nature than platforming.
Level design is Metal Storm's strongpoint. Each level introduces a different gameplay element and is just a unique as the last - save for the first level which is a simple side-scroller but does its job as the introductory level and shows off the uses of gravity-reversal. Level 4 is certainly one of the more memorable levels as it traps the player in a box and the player is forced to combine gravity-reversal and shooting in a small and dangerous environment.
The problems I see in Metal Storm are slightly nit-picky, but are worth dropping the game down half a star. First off, one of Metal Storm's power-ups allow the player to turn gravity-reversal into a weapon - in that - each time you reverse gravity, the mech the player controls turns into a fireball, killing all enemies in its path. I find this power-up too overpowered, after using each other power-up at least once I was careful not to pick up a single other power-up besides the one that turned me into an all powerful fireball. Secondly, even for an 8-Bit game, some parts of Metal Storm are really disorienting. For the most part Metal Storm looks really good, with smooth animations and interesting environments - but too often complex background art gets in the way of being able to tell what exactly is going on in the game.
As the title says, I truly think that Metal Storm is near-perfect game and it is certainly one of the best NES games I've ever played.