METROID is like a seed, it contains the genetic code for what a Metroid game should be, but is far far smaller.
*******N.B.: This review of METROID contains extremely minor SPOILERS but SPOILERS nonetheless*******
EMERGENCY ORDER
DEFEAT THE METROID OF THE PLANET ZEBETH AND DESTROY MOTHER BRAIN THE MECHANICAL LIFE VEIN
GALAXY FEDERAL POLICE
-M510
The above serves as Samus' summons and the player's introduction to the story, all other plot points happen through gameplay. This is what makes the "Metroid" series of games unique. Other video games released at the time -- that contained a story -- advanced their plots with exchanges between hero and villain, hero and victim, hero and helper, et cetera. "Metroid" designer Gunpei Yokoi did not have that luxury, he designed a game with only one human, so Samus did not have the option of delivering quips and one-liners, and it gives the game the sombre tone that has stayed with the whole series thusfar. The story unfolds with the controller in your hands as you kill bosses and dodge shriekbats.
Metroid has the standard controls for most NES games: The 'B' button shoots, 'A' jumps, and 'Select' activates your missiles once you find them. For modern gamers this seems like a short list of verbs for your controller, but one must realize there were only four buttons on the NES controller, and one of them was the 'Start' button. Of course, like any good NES game, "Metroid" throws enough enemies and several unique platforming challenges at you to make it unrepetitive.
"Metroid"'s setting, Zebes(in the original it was called "Zebeth" but that was a localization error) is a very organically-designed world, it contains no artificial breakpoints or any map-like overworld, it simply is designed so that the deadly regions are obfuscated by specifically-designed barriers that Samus can only pass once she finds the appropriate power-up. And there are many hidden power-ups that you would know nothing about without a determination to find them. In this regard the game offers loads of incentive for gamers to try and open every door, enter every room, and find each upgrade; and there are plenty to be had: beam augmentations, missile expansions, energy tanks, and more.
There are five different regions in Zebes: Brinstar, Norfair, Kraid's Lair, Ridley's Hideout, and Tourian. Each contains a significantly different tileset and colour scheme which inspires the feeling of traversing varied and distinct environments. The fact that the creatures found in each region are also quite different adds to this effect considerably. The further you delve into Zebes, the more surreal the environments and enemies become. The corridors are long and disjointed, which frustrates some gamers, but can act as motivation to accomplish the enormous task of infiltrating Zebes and destroying the Mother Brain.
Along the way you will fight two lesser bosses, which at first seem like simple button mashing affairs, but that strategem is ineffective. Eventually the tactics one must employ are more nuanced than the seemingly monotonous combat system would allow.
The game features incredibly atmospheric and eerie background music. Tunes like that which accompany the item rooms antagonize the player into pressing on or running in fear. It evokes the notion that if Samus can complete this mission, she is capable of accomplishing any task she sets out for herself. Moreover, the music gets more intense the further you go into the game, adding palpable tension and intrigue to the environments that are lucky enough to contain the more up-tempo selections.
Unfortunately, some of the sound effects (especially the wave beam) can be pretty grating -- even for the NES -- but thankfully the slightly less irritating ice beam is Samus' primary weapon. Having said that, the bomb explosions sound effectively destructive, the sound effects given to the creatures represent their ferocity well, and the screw attack literally sounds like kinetic energy being turned into a weapon. In short, the sound effects are hit and miss, but the excellent music more than makes up for that.
Despite what most "purists" think, this game absolutely sets the stage for major plot points in every subsequent Metroid game. Many feel as though Super Metroid and the ones that followed were apocryphal to Gunpei Yokoi's original intentions, but the seeds were sown with this game, witness:
1) Metroids which are immune to most of Samus' weapons, but vulnerable to cold: This idea set the stage for the premise of Metroid Fusion.
2) Chozo statues: A mystery at first, but the fact that each statue literally /held/ a piece of unique technology set the narrative tone for Metroid Prime and Metroid II: The Return of Samus.
3) Ridley: This creature embodies the "never give up" attitude. Once you beat him, it is possible to find a secret passage in his hideout that contains his body double. This set the tone for every game that included a version of Ridley (which would be each Metroid game except 2 and Prime 2)
From the above you can see that many, if not all of "Metroid" and "Metroid II" creator Gunpei Yokoi's ideas were preserved and expanded upon faithfully. It is in this spirit that "Metroid" is an excellent series-starter, and a must-play for anyone who's played any of the other Metroid games.
Post-review notes for the reader:
There are several ways to enjoy this classic, even if you don't own an NES. The original cartridge is (I can only assume) extremely expensive on auction sites because of its rarity. Nintendo themselves offer the gamer three additional options.
"Classic NES Series: Metroid" is a standalone game and offers no extra features that each modern Metroid game has.
If you own "Metroid Prime" and "Metroid Fusion" the two can be linked to unlock it on the Gamecube, but with a reversed control scheme to emulate Samus' actions in "Prime" itself.
"Metroid Zero Mission" offers the definitive version with the original controls, but one must beat the game-proper to unlock it.
I urge each reader of this review to figure out which iteration is their favourite. Just don't use a ROM! Emulating is bad not because it's a legal crime, but because it is a moral crime. Whether or not the laws of your country protect the right of the producer to distribute its good as it sees fit, it is wrong to enjoy the product of someone else's labour without giving them their proper due. You will benefit by playing "Metroid", the owner should rightly benefit for providing you with this enjoyable experience.