The structure of a song has to do with how you put certain parts in a certain order. A very typical song structure usually goes something like this:
Intro, Verse, Chorus, Verse, Chorus, Bridge, Chorus, Outro.
The structure of a song is very important. Just as with books or movies, songs need to be put in a certain order for them to flow properly and make sense. With that said, I do not believe there is a certain structure that can be applied to every song out there. Every song is different. And it would get pretty boring if every song had the same predictable order of parts.
The bottom-line is that you need to find the right structure that fits in with the feel or message of your song. Is it a song with which you want to hook the listener right away? Try having your chorus at the beginning. Do you need there to be more “tension” raised before you go to the chorus? Try adding a pre-chorus that appropriately sets the platform for the chorus. Is it a song with which you feel you have to reinforce the chorus’ message one more time? Try adding a double chorus.
The list can go on and on as far as how songs can be ordered in a way that presents a well-paced and effective musical story. However, in the beginning of your writing process, don’t get too caught up in determining the song structure. Doing that would be like naming the chapters of a novel before it has even been written. Your main focus should be to tell your musical story how you want it to be told, and in the order that you think best. Don’t have a strict “radio-friendly” structure that you stick to religiously. There’s nothing wrong with a set structure, but it can limit your song’s uniqueness, as well as your own creativity, if you worry about it too much in the beginning.
My best advice about how to put your song in order is this: Make sure that your song determines the structure, rather than a structure determining your song.