Store Multi Dimensional Data while appending form data with nested append

Question

I have UI in which I can add more with button product which appends field of inputs a type of metal . In which and I can even add more the metal in which it again append data in 1st product field using nested concepts. For example when I first used add more for product with two add metal. 1st time 1product => 2 metal types(contains) using add more metal again add more product 2nd time 1product => 4 metal types(contains) 3rd time 1product => 3 metal types. I cannot add all metal types because every metal group will contain different id.