Well that scene was rather anti-climatic, but interesting...
Head forward and take out the enemies you find until you find metal. We're huge again. Keep going forward following the linear path until you get to fight a saw blade robot. Take out the spear orcs first and then focus on him. It's OK to get hit a bit here. You should also go ahead and use some powers here (we're about to have a lot of sun).
After that you'll see a scene...
Gather up all the sun and head forward. The mine things on the ground are magnet mines. They'll suck parts away from you. They grow bigger and get smaller, so get past them when they are small. North of the third one is a green door. Bash it in and head north, then punch the left wall down here for:
HIDDEN CHEST #42:
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North of the third magnet mine is a green door. Bash it in and head down that path, then punch the left wall to find this hidden area.
Head forward watching out for mines and taking out enemies. You'll soon have no choice but to lose your metal (sad face). Kill the two warhammer orcs past the magnets and continue to a lift. Gather the blocks here and use a super move to take out the robot and orc. To the north in a room is some more relics.
Head onward and you'll battle two robots now. Past that is a sawblade robot and a tank. Take them both out and continue to the left through the door. In here go forward and face the tank. It has a laser beam attachment that is easy to dodge and it also has the shock tank shield. Take it out and continue to a room with two robots and a slime tank (Shockwave is a good attack here).. Between this room and the next room break down the door for:
HIDDEN CHEST #43:
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After fighting the second tank inside the building, break down the door you'll find to the right to find this hidden chest.
Continue on and defeat the robot and tank. Head down for a scene.
Battle Time! Go destroy the shock tank to the left and use it to throw at one of the slime tanks on the right, making it easy to destroy the second one. Two more slime tanks show up from the north, so go take them down. After that is another slime tank and shock tank. Defeat them and you are home free.
Head into the next room and take out the orc, robot and slime tank (I would leave the tank for last). Keep going and you'll fight a shock tank with two orcs. Use a Blast here if you wish and keep pressing on. Fight the shock tank and robots you find (don't worry too much about health) then head north for a scene.
Defeat the saw-blade robot out here then take the left path. Punch the door at the end to find:
HIDDEN CHEST #44:
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After destroying the arsenal, take out the saw-blade robot you find, then take the left path. Punch the wall at the end for this chest.
Head back and go down the straight path now. Destroy the shock tank at the end and then climb up the building that opens up. Up here destroy the slime tank and robot. Break the northwest door open for sunstone, then climb up again for a scene with the doctor.
Head north now and take out the soldiers and tanks you find. Make sure to bring along one of the tank hulls and throw it at the next tank to the north, then mop up the spear orcs (watch out for their wave attack, there is a few of them here).
Climb the building and watch the scene.