Here is a complete guide for Mega Man 4. Choose the tab you want in order to view its content.
Release Date:
Japan: 1991
USA: 1991
Europe: 1991
Developer:
Capcom
Systems:
Nintendo
Genre:
Action

Game Specs:
After blasting Dr Wily's plans three times already, Mega Man was fast beginning to master his fighting skills against the tyrant to become almost unstoppable. Before long, a new challenge arises for the Blue Bomber. A mysterious scientist known as Dr Cossack has constructed eight new powerful Robot Masters in an effort to destroy Mega Man. But this time, Mega Man will be entering the battlefield with an enhanced Mega Buster, this time able to charge up the gun to fire off a stronger shot. A few new special items will help him along the way, as well as trusty Rush. A new character will also make an appearance, Eddie, a small robot that offers Mega Man helpful items in each stage.

Intro Scene:
AD 200X. Household robots Rock and Roll were created by master robot designer, Dr Light, and were enjoying their peaceful days. Then one day, the industrial robots all over the world went on a rampage and the world fell into total chaos. Dr Light quickly realized that mad scientist, Dr Wily, was behind the nefarious deed but he didn't know what to do. Rock, having a strong sense of justice, volunteered to be converted into a fighting robot. Thus the super robot Mega Man was born. Mega Man shattered Dr Wily's plans three times and world peace has been maintained so far.... but history repeats itself. Dr Cossack, a mysterious scientist, has invented eight powerful robots and sent then after Mega Man. Mega Man starts for the battle again, this time equipped with the powerful new Mega Buster!!



 

 
Story:
Dr. Wily is assumed to be dead after his crushing defeat in the end of Mega Man 3. (Groan. I know—bad pun.) A new scientist enters the scene to take Wily’s place after an entire year of peace. This new scientist, Dr. Cossack, claims to be angered at Mega Man and his creator for always overshadowing his own robotic creations. Of course, in reality Dr. Cossack’s daughter Kalinka was being held hostage by the all-too-alive Dr. Wily, who forces Cossack to (attempt to) destroy Mega Man in return for Kalinka’s safety. Luckily for Dr. Cossack, Proto Man frees Kalinka before long—this is lucky because the scientist would never have stood up to the might of Mega Man!
Mega Buster:
This game introduces the Mega Buster, a great new invention which allows Mega Man to charge up energy before firing. A fully-powered Mega Buster shot is equivalent to three normal shots, but if you only power up to the first level, the shot isn’t any more powerful at all—just bigger!
Special Features:
This game introduces the Mega Buster, a great new invention which allows Mega Man to charge up energy before firing. A fully-powered Mega Buster shot is equivalent to three normal shots, but if you only power up to the first level, the shot isn’t any more powerful at all—just bigger!

Picture

Name

Weakness

Receive

Mugshot

Dust Man

Dust Man

Mega Buster/Ring Boomerang

Dust Crusher

Dust Man

Skull Man

Skull Man

Dust Crusher

Skull Barrier

Skull Man

Dive Man

Dive Man

Skull Barrier

Dive Missile

Dive Man

Drill Man

Drill Man

Dive Missile

Drill Bomb

Drill Man

Toad Man

Toad Man

Drill Bomb

Rain Flush

Toad Man

Bright Man

Bright Man

Rain Flush

Flash Stopper

Bright Man

Pharaoh Man

Pharaoh Man

Flash Stopper

Pharaoh Shot

Pharaoh Man

Ring Man

Ring Man

Pharaoh Shot

Ring Boomerang

Ring Man

 

Picture

Name

Weakness

Moth

Robot Moth

Drill Bomb

Robot Box

Robot Box

Dust Crusher

Crawlers

Metal Crawlers

Drill Bomb

Dr Cossack

Dr Cossack

Dust Crusher

Giant Metool

Giant Metool

Ring Boomerang

Industrial Robot

Industrial Robot

Ring Boomerang

Dr Wily

Dr Wily Part 1

Ring Boomerang

Dr Wily

Dr Wily Part 2

Mega Buster (Charged shots)

Dr Wily

Dr Wily Part 3

Pharaoh Shot

 
Rush Items:
Rush Coil Rush Coil:
You have this from the beginning of the game. When you use this item, Rush will appear in front of Mega Man and when you jump on his back he will spring Mega Man up to reach higher platforms.

Rush Jet Rush Jet:
You receive this when you defeat Drill Man. This allows Rush to become a flying sled which Mega Man can ride on to fly over dangerous areas or reach higher platforms. Be careful as if Rush hits a wall or ledge he will disappear.

Rush Marine Rush Marine:
You will receive this after defeating Toad Man. This will make Rush become a submarine in water and can carry Mega Man through the water areas of certain stages. Be careful though, as once the energy bar runs out, the submarine will disappear.

Special Items:
Wire Chain Wire Chain:
This is found in Dive Man's stage. After you defeat the second large whale, on the next screen you'll notice a small hole in the floor. Go down the hole and dodge the spikes on the walls as you descend down to this item. The Wire Chain can be used by press up and fire. This will cause Mega Man to fire out a large chain that will reach up and grab onto platforms and then drag Mega Man up to them.

Balloon Balloon:
This is found in Pharaoh Man's stage. After the first long area with the quicksand, you'll come to an area with a large hole in the ground which leads to the rest of the stage. Jump over the hole and continue to the right. You'll come to another quicksand area. Keep going right to find the balloon. This item once activated will create a floating platform which will rise and can carry Mega Man up to higher ledges.
Mega Buster Mega Buster:
The Mega Buster is Mega Man's primary weapon. You will have this weapon from the start of the game. This weapon can cause damage to most enemies encountered in the game. This is the first MM game in which you can charge up the Mega Buster and fire off a stronger shot.

Dust Crusher Dust Crusher:
This weapon fires out a small projectile that flies straight ahead until it hits something. If it strikes a wall or target, the projectile will split apart and four smaller parts will fly out in diagonal directions.

Skull Barrier Skull Barrier:
This will create a protective barrier around Mega Man which will protect him from contact with enemies. If an enemy strikes the field, the shield will disappear and they will take damage.

Dive Missile Dive Missile:
This will fire out a large missile which will home-in on enemy targets and explode on contact.

Drill Bomb Drill Bomb:
This weapon fires a drill-type projectile which will explode and cause heavy damage to enemy targets. You can also detonate the bomb after firing it.

Rain Flush Rain Flush:
This fires a small grenade straight up and then causes corrosive rain to fall in the area and can cause damage to any enemy on screen.

Flash Stopper Flash Stopper:
This weapon freezes all enemies on screen, allowing Mega Man to fire upon enemy targets with the Mega Buster while they are frozen.

Pharaoh Shot Pharaoh Shot:
This fires a small projectile which can cause damage to most enemy targets. This can also be fired in upward or downward directions by holding up or down while pressing fire.

Ring Boomerang Ring Boomerang:
This weapon fires a small ring-shaped projectile which travels a short distance from Mega Man and then returns to him. Any enemy within range takes damage if the ring hits them.
Final Passcode:

The Pharaoh Shot Trick:
The Pharaoh Shot has a few nifty “features” (AKA bugs) which were overlooked during the game testing. Namely, as Procyon Lotor pointed out, you can use it without actually draining any of its energy. Try some of these things:
-Equip the Pharaoh Shot and you can charge up at any time, even before a major battle, while your enemy is busy filling up its energy meter. (This isn’t the case with the Mega Buster.)
-Charge up the weapon so that a giant ball of energy forms over Mega Man’s head. Hit something with it, then switch to the sub screen without letting go of the fire button. Keep holding the button down as you switch back to the game. The shot will begin to charge up again all over again, without any loss of weapon energy.
-Use this technique against Dr. Wily to defeat him more easily. Whenever he appears, jump up and hit him with the ball over Mega Man’s head, then use the above trick to get the ball back without losing energy. This way you never have to worry about running out of Pharaoh Shot energy in the midst of the battle.
-Some minor enemies will not cause the ball to disappear at all. Use this to your advantage. Find a spot where enemies are coming in high (like the homing missiles that the Hippo fires) and simply stand there, letting the enemies hit the ball and drop their power-ups directly onto Mega Man. Stick a chair leg on the fire button and go eat dinner. When you come back you’ll have full energy and a ton of 1-Ups. (Thanks to OmegaWarrior for this bit.)
-One interesting glitch: If you’re charging up the Pharaoh Shot, you leave the ball behind when you die. I defeated a boss after perishing once because it walked into the ball that had been left sitting in space.
Ending:
This was one of the first games where Wily’s fortress blows sky high, but certainly not the last.
The cloud resulting from the explosion is in the shape of a skull...a cute joke that’s a little overused later on...oh well. Basically, Dr. Wily begs for a bit, then alarms start going off. Wily jumps up and escapes through a secret door. Mega Man teleports out. Then you see the fortress from the outside Wily’s saucer flies away just in time for the castle to kabooom!
Mega Man rides home on top of a monorail car (he always rides on top...saves fare, I guess!). He has his helmet off the entire time. Rush and Roll meet him when he arrives at his “stop” and the screen freezes there. Credits scroll (to Mega Man’s theme song again!). At the end, Eddie appears to toss out the letters that spell CAPCOM. Then he stands there blinking until you hit RESET or turn off the power.