What is the definition of gothic or emo and where it come from?

Recently, at my place(city in malaysia) this new trend(gothic) and fashion are growing. Some said it's due to the influence of blackmetal and religious movement and free social life(is it true?) and teenager age below 18 are becoming their follower of this gotharmy. This worrying me so much because most of this follower is teenage and their religious is muslim, buddhist, and etc. This will change their perspective about their religion. This is not for my own sake but for all Malaysian's sake. The teenager is short minded and they said they only pose the trend but who know's what behind those all weird signs and symbols. I don't want the effect of this trend will become long term effect that will change and destruct family organisation. I need the answer of this problem as soon as possible. Thank you for your cooperation. Do this for the sake of humanity.