Reg.New material type creation

Dear Friends

In what suituation we will create new material type.

My answer is, material which is to be used is not belongs to existing material type in SAP,so we create new material type.

examble ,take button, button is to be attached with garment, after all the process garments will be despatched as finished product.

so,we create new material type as "Accessories", is it correct ?