How to get my song secured
It’s not possible with Mp3tag (and I don’t know of any tool that does such a thing).
Metadata can always be deleted or altered.
If you want to "secure" the audio part of your song in the sense of being able to identify it at any time, you could look into existing audio watermarking solutions.
Unfortunately, I don't use such solutions myself, so I can't recommend a particular one.
If you want to "secure" your song so that it can't be resampled or remixed:
As far as I know, this is not possible.