Maverick likes to live dangerously. He likes fast jets, chasing girls into their bathrooms, and… motorcycles. Of course.
Maverick's motorcycle shows up throughout the film, and it's sort of like his land-based jet. It's sleek, fast, and dangerous, just like Maverick. Here's another thing: Maverick never wears a helmet when he's on his motorcycle, and it always looks like he's going way faster than he's supposed to. (Never mind the fact that California has a very strict helmet law that has been in effect since 1985, thank you very much.)
We see Maverick's motorcycle when he first arrives at Top Gun, when he's racing to Charlie's house for his first date with her, and shortly after he, Goose, and their girls party it up at a bar. We even see Maverick and Charlie making out on Maverick's motorcycle.
Exactly What You're Expecting
The motorcycle symbolizes speed, danger, and sexiness, plain and simple. Maverick is the only male character in the film who's seen driving anything other than a jet, and this is for good reason. He's an unconventional dude, and the fact that he insists on riding a motorcycle at high speeds with no helmet reiterates that fact.
In addition, the motorcycle is fast, sleek, and sexy, and it's meant to make Maverick seem appealing in a very dangerous way. He's the kind of guy who's a little rough around the edges, but still all kinds of desirable, and his motorcycle reinforces that image.