Fly to Metropolis and Find Dr. Nefarious are missions in Up Your Arsenal taking place in Metropolis, Kerwan. Ratchet learned from the Qwark vid-comic Deja Q All Over Again that Dr. Nefarious had previously invaded Metropolis, but Captain Qwark stopped him. From this, Ratchet concluded that Nefarious would attack Metropolis there. After flying there, he found that tyhrranoids were already attacking the city, and aimed to find Nefarious and confront him.
No new weapons are available at the Gadgetron vendor, though the Aegis Mark V armor is available at the Starship Phoenix. If you have money to spare then either that armor or any remaining weapons will be a good purchase. Though the Annihilator, Rift Inducer, and Disc Blade Gun are usually the best choices, as these are your strongest weapons, it is also possible to rely on high level versions of older weapons such as the Agents of Doom, Miniturret Glove, Flux Rifle, Lava Gun and the Suck Cannon.
The mission begins with a fairly linear path across a set of towers. In the first, you will encounter one-eyed tyhrranoids, three-eyed tyhrranoids, and 'noid commanders. On the bridge past the first tower, a tyhrranoid dropship will reveal itself and fire. Dodge its lasers and destroy it, then proceed to the next tower, where more 'noid commanders and three-eyed tyhrranoids appear. Defeat them and use the vendor, and after heading forward, a cutscene will commence.
After this, all the tyhrranoids are transformed into robonoids. Though they are visually different and slightly tougher enemies, they are nonetheless fought with the same strategy as before. This section can be challenging, so if you are having a hard time, consider returning to the Starship Phoenix for better armor, which can be financed with the Aquatos sewers or Annihilation Nation challenges.
You will first be confronted with a group of one-eyed robonoids and three-eyed robonoids. After this, a tank bot will appear, which is a tougher enemy that fires several fast-moving missiles and uses a flamethrower in closer range. Carefully dodge the missiles by side flipping, and use the Annihilator against it, then head right up the ledge where you will fight three-eyed robonoids and robonoid commanders.
Head left, down the grav-ramp, where you will encounter more three-eyed robonoids, and as you progress forward, the windows above will smash and two robonoid commanders drop down. Defeat them and proceed forward, where a tyhrranoid dropship will be encountered alongside two robonoids. After they are defeated, head left, and try to destroy the tyhrranoid dropship before it can deploy any tyhrranoids, then head left again across the grav-ramp.
This grav-ramp can be particularly tricky, as several enemies appear across it, and it is very narrow. Use the Annihilator or Disc Blade Gun here. At first, three-eyed tyhrranoids will appear, which can sustain considerable damage before being defeated. Next, two robonoid commanders will fly in, and it is important to make sure they stay dead, as after dropping, it is possible that they can land on the surface behind them and continue to attack, along with other three-eyed robonoids on the same surface. Head forward once more and defeat the three-eyed robonoids, making sure not to pass over until after they have finished firing, and then climb down the grav-ramp onto the last surface.
After defeating the enemies here, equip the Refractor. Connect the laser beam to the reflector, then use the bolt crank to move it, and then connect the reflected laser beam to a receiver port in the wall on the building. This will create a bridge across to a plaza, with a few more enemies and one final tyhrranoid dropship. Defeat them, and then head forward for a cutscene to commence. This will conclude the mission, and it will continue in "Defeat Giant Klunk".