Assalamualikum wa rahmatullahi wabarakaatuhI see many men wearing metal or plastic or rubber rings on their hands/wrist/arm. In my country women do not wear rubber rings on their arms.What is the ruling on this??

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Wearing bracelets of any kind [metal, or plastic, or rubber, etc.] is a matter peculiar to women. So it is not permissible for a man to imitate them in this. Anything that is customarily known to be peculiar for women, then men are prohibited from it. {C}{C}

Ibn ‘Abbaas narrated: “The Prophet cursed men who imitate women and cursed women who imitate men.” [Al-Bukhari]

The Fiqh Encyclopedia reads:

“There is no difference of opinion among the jurists that it is forbidden for men to imitate women in their movements, in being soft in speech, in adornment, in dress, and other things that are specific to them either by custom or by nature.” [End of quote]

It is understood from this that if it is not customary for women to wear it, then it is permissible for men to wear it, as in the case of wearing a bracelet on the arm.

Regarding wearing a ring on the finger; the most correct view of the scholars is that it is permissible for a man to wear a ring provided it is not made of gold. Shaykh Ibn 'Uthaymeen said: “The most preponderant opinion in my view, it that it is permissible to wear a ring of iron, or anything else, with the exception of gold, and that this is not disliked.” [End of quote]

However, we must warn against wearing such things while having wrong and corrupt beliefs and being superstitious about them, such as believing that they bring good luck or repel evil eye and so on, as this is contrary to Tawheed.

Also, it is not permissible for a Muslim to take something as a reason (i.e., a means to realize good or repel evil) unless the Sharee'ah has made it a means, so you must be careful about this. Allah Says (what means): {And if Allah should touch you with adversity, there is no remover of it except Him. And if He touches you with good - then He is over all things competent.} [Quran 6:17]

Allah knows best.