There’s a big difference between a singer who doesn’t have a classically good voice, and a bad singer. Even singers who could never do opera can be amazing vocalists. Kurt cobain was mentioned by another commenter, and … man, listen to the mtv unplugged recordings of him. He put so much energy and feeling into that I still get goosebumps just thinking about it. Others suggested taking voice lessons, and it’s a good idea IMO. Just don’t try too hard to sound like someone else. Learn good technique, how to protect your voice, and then focus on how to put the feeling into it.