Please advise me if mourning – matam – called in my culture Zangeer Zani is a recommended practice – mustahab – in Imamiyyah fiqh. If it is forbidden – haram – and not mustahab, please give me the reason why?

All expressions of matam are approved of, with the exception of acts which endanger life and limb. It is advisable to refrain from those things that displease Allah Almighty, especially when it gives a bad impression about believers’ behaviour.