Judaism is really fascinating and the more I learn about it the more I love it ! I came up with a question because I was born Jewish but I grew up Christian and believed that music is sometimes bad . Does Judaism allow me to listen freely to every music genre I want or does it have a problem with some specific genres ( for example Black Metal ) ?
Hi @JewliusCeasar and welcome to Mi Yodeya.
I think it is worth stating by way of introduction that if you are on your own personal spiritual journey it does make sense to find a mentor to help you with the process (see here). By the same token, I would advise you not to rush the process and do too much too soon. Go at a pace that is right for you otherwise a dramatic change in lifestyle can prove to be too overburdening.
I will start by detailing some sources about music that will help to frame the Jewish outlook.
It writes in the Gemara in Brachos 6a the following:
בִּמְקוֹם רִנָּה — שָׁם תְּהֵא תְּפִלָּה
In a place of song, there prayer should be.
Whilst this source is a reference to a synagogue where G-d's praises are sung, it nevertheless introduces the concept that song has an innately spiritual side to it.
Indeed within Chassidic thought, song and music represent a gateway to a much higher spiritual attachment and is a means through which one can connect with G-d. One such example in Tanach can be brought in Melachim II 3:15 where Elisha the prophet requests the use of a musician:
Now then, get me a musician.” As the musician played, the hand of the LORD came upon him,
And as the Metzudas Dovid relates there, the music helped bring the spirit of prophecy upon him.
In addition to music helping to forge a Divine connection, it also played a prevalent role in Jewish worship. The Leviim would sing in the Beis Hamikdash, and musical instruments were used and are mentioned several times throughout Tanach and beyond. As Rambam asserts in Moreh Nevuchim (Guide to the Perplexed) Part III, Chapter 45:9:
The object of the singing is to produce certain emotions; this object can only be attained by pleasing sounds and melodies accompanied by music, as was always the case in the Temple. (Friedlander translation)
Finally, even the malachim (angels) we are told, relate to G-d through song e.g. Chullin 91b
So with this in mind let us return to your question....
If we regard song and music as something that has a spiritual strength to it, it does stand to reason that we should try and listen to songs that are meaningful and help us strengthen this connection. Therefore, songs that lack a sense of tznius (modesty) or morality, celebrate idol worship / pagan deities, or songs that use lyrics that are full of obscenities / inappropriate content obviously run counter to this approach.
Perhaps as Rav Nachman of Breslov best encapsulates in Likutei Moharan 3:1 (hat tip to @Yehuda):
Behold! when someone listens to the singing of a singer who is wicked, it is detrimental to his serving the Creator. But when he listens to a singer who is virtuous and worthy, it helps him
I hope this helps to begin to answer your question and I wish much hatzlacha (luck) with your journey going forward.