ANSWER:

If they are going to apply henna on the man, this is not permissible for you to attend it. 

QUESTION: I’m being invited to a mehndi function where there is going to be segregation between men and women. There is going to be no music in the men’s section. However, music will be played in the women’s section. Me being a male, if I go to such a function will I be sinful? Considering there is going to be no music in my section