When this stage begins, you're in a room with special item refills and item canisters. Collect any goodies you need, and then you can drop down to the room immediately below. Guess what? You're already to this stage's boss!
You've finally made it to Dr. Wily, it would seem. When the battle first starts, stand along the left side of the screen. A giant tank will plod onto the screen, held up by pin-shaped appendages. The first target is the cannon attached to the machine's belly. You can take it out with well-aimed flurries of fire from your standard arm cannon.
By the time the machine is at the screen's center, you should have laid waste to its life meter. Once the meter is empty, the bubble over the top of the machine will pop off. Slide under the robot leg and stand directly below the bubble, then just start chucking shadow blades upward. They should make quick work of the second life meter.
Note that you may need to use an energy tank if your life runs low during the process. But if you work quickly, one tank is all that will be necessary. When you win, you'll find that a robot was at the controls. There's one more stage to go before the game's closing credits.
NEXT: Stage Six