Defeat Mecha-Ridley and escape the Space Pirate Mothership to unlock the original metroid option. You may play the original Metroid by pressing options and selecting Original Metroid. Have fun!
To actually inflict damage to Kraid, you must first shoot him (either with a charged shot or with a missile) in his top eyeball. He will open his mouth and scream. When he does that, you can shoot charged shots or missiles in his mouth. After you wear him down somewhat, he will change colors. When this happens, his strategy also changes. He will destroy all of the blocks beneath you, except for one. He also moves closer to you and begins to use one of his arms to block shots/attack. When you shoot him in the head to open his mouth now, you only have a narrow window of opportunity to shoot his mouth as he raises his arm up. More than likely, you will be hit by his arm or claws. On his last stage, he will destroy the last block and you have to stand on the things he shoots into the wall. When you begin to run low on missiles or health, move to the ground. Avoid him moving forward, and shoot his claws when they get close. They will turn into health/missiles. Unless the claws hit you, you are otherwise invincible. When you have enough health/missiles, simply jump back up.
Defeating The Larva In Norfair
When you are in Norfair after defeating Kraid, you will eventually encounter a larva that you cannot pass, he blocks the way. When you have the Varia suit, you will be able to go around. You will obtain the Wave Beam as well. You will reach a room that is more or less impossible to get out. The door turns to gray behind you. The path above you is blocked by a larva. You can destroy it with the Wave Beam by getting underneath it (on the level below) and shooting its belly. After you defeat it, you will move to the east, only to find a larva charging at you. To defeat it, fire Missiles, Charged Beam, or the regular Beam multiple times to push him back. After he passes the little plant (long and oval shaped on the ground; you can walk through it), morph into your ball and wait. He will buck up and start to charge. Just before he hits you, plant a bomb and roll to the east. If timed correctly, the bomb will explode under his belly. You will be able to tell if it works as he will take damage. Repeat this until he dies.
To defeat Ridley much easier (this is also very helpful under the hard difficulty setting), hit him with missiles until he starts to move closer. Then, jump into the lava and shoot him again with missiles while he is above you. You will receive minor damage from the lava, but it is better than taking massive damage from his fireballs, grab, and tail attacks.
Defeating The Underground Worm
The only way to defeat it is to use your missals. When the Underground Worm opens his eyes, immediately shoot it at least once before it closes. Do this two more times to defeat it. If you are not quick enough to defeat it, it will run away. Also, if you defeat the first Underground Worm, you will get the Charge ability.
Brinstar Super Missile
In a hidden area of the first long, vertical shaft in the Brinstar area, there is a Super Missile Tank under a low passage filled with charge blocks. Initially, it looks impossible to attain this item, but there is a way to get it, after you get the High Jump item. Roll into Morph Ball form through the low passage to the right. Note where you appear on the screen. At the same level on the right-hand side of the screen is another ledge. Get to this ledge and go right, bombing your way through the room with the two Rippers and coming back up to the surface in front of a door. Stand with your back against the wall, and wait until the bomb block returns, then shoot open the door and run to the right. Continue running until your Speed Booster activates, then immediately press Down to store the charge. Run back to the left, quickly shooting open the door, and in the 'dip' in the floor level before the door, roll into Morph Ball form and press A, then Left. If done correctly, you will blast to the left, crashing through some charge blocks in the next room, and destroying both Rippers on your way through the hidden room. After you leave the hidden room, as the screen is scrolling, you should hear the Speed Boost sound effect start again. Immediately hold Down until after you appear on the next screen to store your charge again. Roll out of the hidden passage, jump onto the lower platform, then press A, then Left again. If you have done everything correctly, you will blast through the hidden passage on the left side of the screen, crash through the charge blocks and collect the Super Missile Tank. Many items in this game can only be attained through creative uses of Samus' dashing attack like this; any time you see an item that is blocked by charge blocks, look for areas nearby where you can build up enough speed to activate the Speed Booster.
Always Have A Full Energy Tank
When you reach a Chozo Statue, roll into the Morph Ball and go in its hand. You will have your energy tank filled. Roll into it again, this time planting a bomb. Go into another room, then return to the room with the Chozo Statue. Roll into the hand, and you can heal Samus again. Repeat this as many times as desired.
Morph Ball Jump
Once you get the Morph Ball Bombs, you can get to some high places that would normally require High-Jump or Space-Jump. Get into Morphball and start laying down bombs. You will bounce when they explode. Keep pressing A repeatedly and you can go as high as desired. This requires some patience as you may fall often.
Fly With The Morph Ball Bomb
To basically fly in Morph Ball form, first get the Morph Ball Bomb. Then quickly tap B. The bombs will eventually carry you straight up. This is a quick way to get up to high places without repeatedly jumping.
After running far enough to activate the Speed Boost, press Down to temporarily store the energy. Samus will continue to flash and can perform a dash attack by pressing A, then the direction of the charge. Samus can also dash in Morph Ball form. This charge can break Speed Booster blocks to reach items that are otherwise unattainable.
Get Out Of Chozodia
After you get the Gravity Suit back and get the Power Bombs, you can go back to Brinstar, Kraid, Norfair, etc. with the new upgrades. Go to Chozo Ruins (green unmapped part) and to the lower part. You can get a Super Missile Tank. There is a long path that leads back to Crateria. You can use the Power Bombs and get more items. You can travel back and forth to Chozodia if desired.
Original metroid game
To play the original NES version of metroid complete the game succefully. Look in the options menu for the game. Also, look for the newly added "Gallery" option.
Beating Steel Riley
To beat steel riley at the last level you have to shoot his chest it has a glass case. With a heart in it that is how you defeat him.