Throughout each level, you'll find dozens of different enemies and several types of weapons that you can use to fight them. For most of the time, you'll be fighting enemies and changing weapons, the effectiveness of which depends on the situation you're facing.
That said, the most surprising thing in Legendary Wings is waiting at the end of each level, when you have to fight the respective final bosses. These come in all shapes and sizes (some are dinosaurs, others seem to be Evangelions or giant robots); they are a far greater challenge than normal enemies, and you need to use all your attack power against them.
Legendary Wings is an outstanding spaceship arcade game. It doesn't have particularly good graphics, but it still offers a tremendously addictive traditional arcade experience.