Songs and tunes can have all sorts of structures. There are some conventional ones (listed below), which help both the writers/performers and listeners classify, recognise and get comfortable immediately with songs new and old.
You have the classic Verse/Chorus structure and variants of it (eg Penny Lane/Happy/Hotel California)
The AABA form of many jazz standards (Somewhere Over the Rainbow/Yesterday/The Way You Look Tonight)
The AABB form of many traditional Irish tunes.
Verse/Verse/Verse and so on with no chorus (eg Heartbreak Hotel/The Boys of Ballisodare/Amazing Grace)
The more recent pop structure of Verse/Bridge/Chorus (eg Perfect/Piano Man/Someone Like You)
And then you have pioneers who create new structures!
This is my favourite tune from our album Melodic Reflection – The Reel Movement (written by Seamie).
He may correct me, but I make the structure to be Intro/ABCCDDC/Intro/ABCCDDC/Outro…enjoy it everybody.