Sometimes an absolute diamond of a game comes quietly along, slips under the radar and is tragically overlooked by the majority of the gaming population. Metal Arms: Glitch In The System is one such game and if you're yet to experience its joys then you really should hunt down a copy, because you're missing out on something very special.

The story begins with a hilarious World War II style documentary, complete with whirring black and white film and unstable sound, narrated in that inimitable Forties style. The setting is actually planet Iron Star, a futuristic world populated entirely by droids, but the whole story subtly parodies WWII to great effect. The Droids are under attack from the evil and insane General Corrosive, a giant droid created in an experiment gone wrong by renowned scientist Dr Exavolt. Manufacturing an army of Droids loyal to him, known as Milbots, Corrosive is determined to conquer the whole of Iron Star and the robot resistance against him isn't going well. This is where you come in as Glitch, a robot with strange markings found in the ruins of a city district. He's taken back to HQ and fixed up, then put straight to work for the resistance.

You begin your first mission in the mines, accompanied by two resistance fighters, named Hosed and Screwed. The action is third person and Glitch is a speedy, manoeuvrable character, double jumping around with plenty of inertia for making those death-defying leaps across gaping chasms. Your comrades guide you through the mine, which serves as a brief but exciting tutorial level, where you master the basics of your mining laser and core charges (grenades). However, this is only the very beginning, as the game is huge and full of so much variety and imagination that there's no way I can mention even half of it here. I'll try though.

There is no doubt that you will be quickly struck by the excellent quality of the graphics, in both detail and design. Even in mines, a potentially dull location, there are glowing crystals, huge explosions and industrial plants filled with sophisticated looking computer banks and mining machinery. After the first level, which you complete by gliding down a long zip line, your comrades are sadly killed and you're on your own. The second level sees you infiltrating the Droid mining facility with the intent to blow it up before the enemy overruns it. If you're observant, you'll find that the main entrance isn't the only way in - there are vents that can be shot open and climbed into. Walking around in the ventilation system, you find multiple paths for getting around the sneaky way, poking out to shoot the Milbot grunts, then carrying on through the vents. You can even find your way into the prison cells and rescue three droids to assist you on the way! This kind of variety and flair is present in every level of the game, in fact there is so little repetition and it's such a huge game that I really don't know how they packed so much in.

Once you're out of the mines, you must fend off the Milbot attacks on Droidtown before heading on an epic adventure across Iron Star to rescue Dr. Exavolt so he can stop General Corrosive once and for all. Beyond Droidtown lie desolate wastelands; an endless scrap land infested with zombie-droids. These things are one of the creepiest enemies I've ever played against, even though they're only robots! They charge along at great speed and when you shoot them, they shatter into about fifty pieces of wreckage. However, give it a couple of seconds and they come back to life, the pieces rising up and reassembling before your very eyes - it's an eerie effect and a great touch to have them in the game. They're very much like Halo's Flood, as although they can't infect other droids, they'll go for the Milbots just as much as you, so you can lead zombies to Mils then get out the way and watch the fireworks. Indeed, watching the cowardly Mils running around and screaming as they get destroyed is most satisfying.

On your travels you will head deep inside the planet, where you are greeted by the most amazing sight - the gigantic Morbot city, a relic of a bygone age. It looks ancient yet advanced, with some of the coolest graphical scenery I've witnessed in a game - think Halo's ancient Forerunner technology but weirder. The way the various doors open and bridges build themselves block by block in front of you, the impossible engineering keeping the Morbot city running, it all looks amazing. The music in these parts is perfect too, an evocative score that completes that otherworldly atmosphere - a real feat for a game already set on a world other than our own. Beyond the Morbot city lies the Mil city and Exavolt, although that isn't the whole story and the game keeps on going long after you're expecting it to finish - but not in a bad way, as the twists and new challenges are always very entertaining.

As I've already touched upon, the variety in the game is simply staggering - so much so that you never get bored. Every few levels you'll come across something completely different - there are several racing levels where you drive an armoured truck across the wastelands against the clock, or you man the gun while someone else drives for an on-rails shooter level. In one part, you must defend a fortress from enemy attack until reinforcements arrive, using one stationery gun to blast everything that approaches - a very tricky level. There are also levels where you play as different characters, including a giant droid that uses an iron girder to smash the enemies flying and a very anxious droid with a flamethrower!

Each character is as funny as the last; indeed, Metal Arms is one of the most consistently amusing games I've ever played. The script is razor sharp and wonderfully acted all around, with a host of likeable and larger than life characters. Colonel Alloy, the leader of the resistance, is your typical British Brigadier, while Krunk the mechanic who looks like he's half reconstructed from spare parts, is bad-tempered and foul-mouthed, such that there are frequent bleeps in his dialogue (although you can easily tell what he is saying, the censoring is timed perfectly for maximum comic effect). Krunk and other characters, including undercover operative Agent Shhh, are voiced by none other than Dan "Homer Simpson" Castellaneta, so you know you're in for a real treat. The Milbots are all voiced well too, shouting during battles and releasing gas from their butt plates when afraid.

I've got all this way without even mentioning the weapons - and there's a collection here that upstages most first person shooters. Machine gun, scatter blaster, mining laser, ripper, rivet gun, rocket launcher and many more await your shooting pleasure, plus an assortment of grenades. While they might not sound like much, each weapon has three levels of upgrades that you purchase or find as the game progresses. Each weapon looks so much cooler and is more powerful when upgraded, so getting them all maxed out becomes something of an obsession. For example, the rivet gun fires super-fast rivets at the enemy. The level 2 upgrade makes them explode and the level 3 upgrade allows you to hold down the trigger to charge up a more powerful explosion, then release to let it rip. It's hilarious watching a Milbot run around with an arrow through his head, watching the tip glow brighter and brighter, then letting it rip. Each weapon gains enhancements and sometimes extra abilities as you upgrade them, be it speed, power, ammo capacity or other factors.

Every weapon looks lush and the way Glitch's gun hand transforms as he swaps weapons is niftier than Ratchet & Clank's finest weapons morphing - it's like watching a mini-Transformer in action and I never grew tired of watching those animations. On the grenades front, alongside coring charges are cleaners (powerful missiles that home in on up to three targets), EMP grenades for shutting droids down and recruiter grenades, for reprogramming the enemy. Yes, that's right, you can turn most bots to your side with this amazing device, which creates an energy ball for a few seconds and all bots close enough to it are recruited to your team, becoming your allies and fighting on your side. If you get a couple of the bigger droids with you, it can make all the difference between victory and death.

And there's more! A catapult to fire your grenades (getting a distant flying enemy with a recruiter grenade is so satisfying, as the aiming is all about judgement) and the tether, a device that allows you to take control of enemy bots! Even better than recruiting, you can go inside a robot and run rampage. Over the levels you'll have the chance to become about eight different kinds of bots, including ones that fly and big ones that can crush smaller Mils underfoot - it really is fantastic fun. You can lock onto any droid with its back to you, be it sleeping, walking around or shut down from an EMP grenade. Throw in armoured cars to drive and tanks to use in some levels and you'll begin to see why everything stays so fresh throughout the game. There's even a level where you have to dismantle yourself in the Milbot factory, then get rebuilt to pose as new Milbot! In one part of the level you have a game of Simon Says as part of your training and it's easy to make a mistake and get caught out. There are boss encounters too, including one of the most spectacular and extended boss battles at the end of the game, spread across two levels.

I've already mentioned how great everything looks, but one of the best things is the explosions and the way your enemies are destroyed. In most games enemies fall down dead or fade away but not here - every robot explodes in a shower of flames and pieces of metal, their component parts scattering and bouncing everywhere. Sometimes the legs survive and continue running around! While the smaller robots look great, the bigger ones look superb and when you see one of the big, chunky Titans explode for the first time, you'll be amazed. The scenery explodes with plenty of fire and debris too and you can blow up computer terminals, street lamps, oil drums, gas tanks and much more.

The explosions are so flashy and the sound so meaty that I found myself destroying the scenery a lot just to see it explode - this and the fact that much of the scenery contains washers, which are used as currency. There are a couple of dodgy geezer droids (!) hanging around almost everywhere you go and they sell you upgrades, ammo, grenades and health, if you've got the washers. The big guy takes out his folding table and spreads out the merchandise while the little guy gives you the patter - it's one of the coolest ways to buy stuff I've come across in a game, but then that could be said for so many aspects of Glitch.

Sound wise things are perfect - the weapons effects are outstanding, the explosions are loud and booming, the voice acting is charismatic throughout (helped by the very witty script) and the music is as ranged as Halo. While not as epic (nor trying to be), it covers a real range and comes up with a number of really catchy tunes, as well as the more atmospheric and ambient music for the grander levels.

To up the lifespan, there are over a hundred secret gold chips hidden throughout the single player campaign. Collecting these unlocks the multiplayer levels and most levels can be played through against the clock to unlock more chips too. On the multiplayer front, the range of weapons, vehicles and bots to possess in multiplayer makes it a hell of a lot of fun. The only drawback is that the level designs aren't up there with the genius of classic shooters like Halo or Unreal; they're good and some are great, but some are quite weak too.

So, is there anything wrong with Glitch? Very little - Glitch's inertia can be a double-edged sword and a few annoying fall to your death moments can occur. Still, there are regular automatic checkpoints, so you'll never have to go too far back. Other than that, it's flawless down to the lovely presentation - even the animated loading screen is super cool!

Metal Arms: Glitch In The System is one of the finest games to come out in this generation and one of the most underrated ones too. Spectacular graphics and superb sound, a sprawling adventure packed full of neat touches and cool weapons, great humour and an accomplished multiplayer; Glitch embodies what games are really all about - challenge, entertainment and fun. As such, it really deserves a place in every gamer's collection and by now you should be able to pick it up at a real bargain price. Go on, grab a copy and put a Glitch in your system!

Reviewed by Geoff Holland for AceGamez (All Rights Reserved).