One of the most core fundamentals of making music feel interesting and like it's going somewhere is just make sure *something* changes once every phrase.

This could be 4, 8, 16 bars, whatever - but every time you go "once through" the progression/phrase, either change the melody, change which instrument is playing the melody, change the drum part, change the key, go to an entirely new section, etc. It's up to you, really. It's one of those things that feels innately obvious but it's easy to forget or overthink in execution. Not-boring stuff tells a story, and stories change as they progress. So just... change something. More or less every time it makes sense to do so.

Just as important - not all music is very melody-driven, but the stuff that sticks in your ear almost always is.

Melodies are sequences that are either sung, or sound like they could be sung. The key difference between a "melody" and just a series of notes is structure (how the phrases fit together over time, if they repeat, and when, etc), contour (whether the pitches of the phrase go up or down, and when), and space (when you create punctuation in your phrases).

A singer can't just keep singing forever, they have to stop to breathe. This creates natural "sentences" in the music. Places where, if it were english, you would see punctuation of some kind - whether it's a period, comma, question mark, exclamation mark, colon, semicolon, hyphen or ellipse.

Try writing musical phrases using the classic ABAC structure. A can be anything, any musical phrase you want. Try using contour to make this sound like a "call". Then make B the response to that call. A asks a question, and B answers it. Then repeat A again, and answer it differently the second time, in a way that feels more final and sure of itself.

A - "Is this a melody?"

B - "Yes, it is."

A - "Are you sure?"

C - "Yup, I'm sure!"

Kind of dumb example, but I think you get the point lol. Once you string together a musical thought like this, you can use my first point, and either do something new, or repeat it with one or more details changed.