Is rap music haram? There is a kind of rap music that doesn't have any melody in the background. Who decides if it can't be played in amusement gatherings? Is it up to me to decide?

We have hadiths that state that “ghenaa’” is haram, and ghenaa’ in Arabic means to sing (what singers do). If in the society that you live in rap is considered as singing, then it’s haram. As for the music part, if the type of music is one that is generally found in entertainment gatherings (like concerts and discos) then it’s haram. This is designated by your society. If most people in your society consider it as “entertainment” music then it’s haram.