Metal Harbor is the fourth stage of the Hero story in Sonic Adventure 2. It is playable by Sonic. As the name suggests, the harbor is indeed built of metal, and consists of many shipping yards and aircraft launch sites scattered around the place.
Sonic the Hedgehog must escape Prison Island after being freed by Amy. G.U.N. is aware that Sonic has escaped, and several bomber planes have been scrambled in an attempt to impede his progress. Sonic hitches a ride with a missile in order to escape.
Unsurprisingly, the construction of the harbor leads to an abundance of rails, all of which can be grinded on. The frantic charge through the harbor eventually culminates in a hectic race up a missile gantry, forcing Sonic to find a spot to latch onto the missile before it launches and destroys the very ground he was standing on. He then jumps off the missile, and goes through a tunnel on a board, gets out of the tunnel, and rides on a Snowboard inside a loop-de-loop to get to the goal ring. As Sonic races through this zone, he encounters many G.U.N. bots trying to stop him from escaping, as well as jets.
Level Up Item
The Level Up Item in Metal Harbor is a major level-up item, called the Light Shoes. These allow Sonic to move along a trail of Rings at super speed. The player is required have to get this level-up item to complete the game. The move unlocked is called the Light Speed Dash.
Escape from the military base
Sonic is freed from his cell and can now get away from the base. This stage is fairly easy but there are parts where Sonic must use the Light Speed Dash and Homing Attacks to get across gaps. During the rocket part, Sonic can quickly take the shorter path to get onto the rocket and he will then slide down inside of it. Afterwards, Sonic will reach the Goal Ring to complete the mission.
Collect 100 Rings
Note, to make this mission even easier and quicker, Sonic must get the Bounce Bracelet from Pyramid Cave first. This 100 Ring mission is very easy as most of the rings are out in plain sight. And there are many rings that Sonic can Light Speed Dash across. In the large area with the boxes, Sonic can collect Rings inside and use the Bounce Bracelet to get to the higher ones.
Find the lost Chao
Like all "Find the lost Chao" missions, Sonic will need the Mystic Melody but will also need the Bounce Bracelet. This mission can be tricky due to where the Chao is located. In the area with the boxes, Sonic must bounce himself up to the Ancient Shrine and play the Mystic Melody. This will cause some platforms to appear and Sonic can jump to them. Sonic must then carefully jump over some more platforms to get to the lost Chao.
Reach the goal within 2:00
This is a very strict time limit to complete this level. From the beginning, Sonic should immediately Light Speed Dash across some Rings to cut off time from this level. Sonic should then quickly run through the level ignoring the G.U.N. robots and quickly running up the rocket.
Complete Hard Mode
Not much has changed in this level except for the increased number of enemies. However, there is no longer a larger rocket to grab onto and Sonic must, instead, Homing Attack across some enemies. Otherwise, it is simple to earn a high score and complete the level.
After the first Point Marker and bouncing off the set of two Springs, the player will land on another enclosed hallway. Climb onto the roof, perform a Homing Attack on the enemy to the right of the player, and then perform another to reach the fuel tank behind him, where the first Chao Container is.
The second Chao Container is in the middle garage on the left-hand side of the air-craft carrier.
The final one is located to the right of the third Point Marker.
Big the Cat sighting
Big the Cat is seen fishing near the last Point Marker of this stage.
The missile that Sonic grabs on to has two hold spots but the higher one is a little harder to get to due to the limited amount of time. The easiest way to get the A rank is to grab the higher missile, however, it is possible to get an A rank using the lower way by scoring enough points in the rest of the level.
In the original soundtrack for Sonic Adventure 2, there is an electric guitar instrumental intro in the BGM. This has also been included in later games that features the BGM as well; however, in the game, it doesn't have this addition.