Transformers: Beast Wars Metals 64 Cheats - Nintendo 64

Ravage and Tigatron
Select vs. or arcade mode. Highlight Cheetor, then hold [Z] and press [A] at the character selection screen. Then, press [Left] or [Right] to go through his colors to get to Ravage and Tigatron.

Starscream
Select vs. or arcade mode. Highlight Waspinator, then hold [Z] and press [A] at the character selection screen. Then, press [Left] or [Right] to go through his colors to get to Starscream.

Black Arachnia
Select vs. or arcade mode. Highlight Tarantulas, then hold [Z] and press [A] at the character selection screen. Then, press [Left] or [Right] to go through his colors to get to Black Arachnia.

Original Rattrap
Successfully complete the game, including defeating Megatron X. Select vs. or arcade mode. Highlight Rattrap, then hold [Z] and press [A] at the character selection screen. Then, press [Left] or [Right] to go through his colors to get to his original appearance.

Alternate costumes
Select one of the following characters and press [Left] or [Right]. Optimus, Trantulas, Airazor, and other characters have a strange Blue form.

Opimus Primal: Him with Predicon symbol (in beast mode).
Rattrap: Odd Rattrap.
Cheetor: Tigatron look-alike.
Airazor: TigerHawk Look-alike.
Megatron: Transmetal 2 Dinobot look-alike.
Terrorsuar: Old Terrorsuar (colors)

Fight Megatron X
Successfully complete the game with Megatron with no time limit. You will have to fight Megatron X at the end.

Defeat Megatron X
Press [C-Right] to keep firing your gun until you get a Energon Strike. Transform into vehicle mode. Then transform into beast mode and keep pressing [C-Right] rapidly until your Energon bar is filled. Get close to Megatron X. Repeat this you defeat Megatron x twice.

Another advantage happens when both of you shoot something at the same time, after you fire block. Your shot should hit and his should do minimum damage.

Metal Megatron
Defeat Metal Megatron in arcade mode to unlock him as a playable character.

Easy win
For an easy win, transform as in vehicle mode. Run/fly around the arena and keep pressing [C-Left] or [C-Right] to use good weapons. Then, when your enemy is half way down in HP, turn into robot mode, hold [C-Left] for about fifteen seconds, and release. Your character should do a strong blast and should defeat your enemy easily.

Glitch: Robot watcher
Play on the Ice stage, and look at the background closely. You should see a robot that is watching you. Note: This does not happen very often.