Megatron starts the fight in his jet form and shoots up to two rounds down at you. Use your shield to avoid them. After two rounds of firing, he will land and start ramming. You cannot hit him while he is still focused on ramming. When he stops ramming and stands up in one place looking around, pick up any car and immediately throw it at him. If not done fast enough, he will return to ramming. If that happens, wait for him to stop again. If done successfully, he will now attack you. Hit him in close range combat with your melee attacks until he returns to being a jet. Again, after two rounds of firing, he will return to the ground. In his second attack, he will use his ball and chain. Toss another car at him. If done successfully, he will attack you again. Use melee attacks on him. Once again, after a couple hits he will become a jet and fire at you. Do same as before to avoid that attack. After firing at you, he will go back to the ground. His third attack is the flamethrower. Be cautious as it will be difficult to get cars to throw at him. When he is hit by a car you threw, he will attack again. Use melee attacks on him. For the last time he will become a jet again. Use the same strategy used earlier to avoid the attack. He will land after few hits and attack you with all the attacks he used previously. Throw cars at him every time after each attack. After that, you will fight him for the last time. Use melee to defeat him.
Go to "The Suburbs" or "More Than Meets the Eye" levels. Go to the power plant to find a Decepticon there, but you can also bring one there. There will be capsules marked "Danger, High Voltage". There are about 100 of them at the power plant. Pick up a capsule and throw it at the Decepticon to cause a lot of damage. This can cause police cars to come at you if you are near the city. There are a few of these capsules also at the junkyard. The same can be done with gas trucks in the junk yard or the gas tanks in the gas station near the junk yard.
During the mission as Ironhide when you help Jazz at housing estate south, you'll confront a Decepticon with a hose. You cannot damage him with melee attacks until you throw something at him. After that, you can pick him up, or when he gets up you can use melee attacks.
Activate the following cheats by entering the corresponding sequences of buttons at the menu with the "Campaign", "Bonus", and "Options" selections. To play with unlockable characters, after entering the code select "Bonus Features" and then select "Generation 1":
CHEAT FUNCTION - CHEAT CODE All Missions - DOWN, UP, LEFT, RIGHT, RIGHT, RIGHT, UP, DOWN. Cybertron Missions - RIGHT, UP, UP, DOWN, RIGHT, LEFT, LEFT. Infinite Ammo - UP, DOWN, LEFT, RIGHT, UP, UP, DOWN. Infinite Health - LEFT, LEFT, UP, LEFT, RIGHT, DOWN, RIGHT. No Traffic, Police, or Military - RIGHT, LEFT, RIGHT, LEFT, RIGHT, LEFT, RIGHT. Play as Megatron generation 1 - DOWN, LEFT, LEFT, DOWN, RIGHT, RIGHT, UP. Play as Jazz generation 1 - LEFT, UP, DOWN, DOWN, LEFT, UP, RIGHT Play as Robo-Vision Optimus Prime generation 1 - DOWN, DOWN, UP, UP, RIGHT, RIGHT, RIGHT. Play as Starscream generation 1 - RIGHT, DOWN, LEFT, LEFT, DOWN, UP, UP. Play as Generation 1 Cartoon Megatron - DOWN, LEFT, LEFT, DOWN, RIGHT, RIGHT, UP Play as Generation 1 Cartoon Optimus Prime - DOWN, RIGHT, LEFT, UP, DOWN, DOWN, LEFT