"Metal catalysts" refers to a type of substance, usually made of metal, that helps speed up chemical reactions without being used up in the process. They are like helpers that make reactions happen faster. Full definition
Morris Bullock edited a book on replacing precious metal catalysts with iron, nickel and other earth - abundant metals (pnnl.gov)
Heterogeneous catalysis involves the use of metal catalysts like platinum to speed reactions, as in the catalytic converter of a car. (sciencedaily.com)
CNTs are often synthesised via chemical vapour deposition, in which hydrocarbon vapour is deposited on metal catalysts under a flow of non-reactive gas at high temperatures. (sciencedaily.com)