What does it mean when a guy sings in front of you?

It is called being serenaded. He wants to go out with you. If he is smiling when he is singing he is definitely interested in you. I would just take it easy. He might ask you to go out, if he hasn't already. Enjoy!

当一个男生在你面前唱歌时，可能有几种不同的含义或意图。这可能是因为他想表达对你的感情，比如喜欢你或者欣赏你。也可能是他只是想展示自己的歌唱技巧，或者是在某个特定的场合（如演唱会、派对等）进行表演。此外，这也可能是一种社交活动，他希望通过唱歌来与你和其他人建立联系，营造愉快的氛围。当然，具体情况还需要根据当时的情境和背景来判断。