Hello Aspirant,

Due to less number of applicants for GATE Metallurgy as compared to other branches, most of the coaching institutions ignore this stream. So there is none. One or two coaching are there but don't trust them. I suggest you buy GATE metallurgy question paper book by Arihant publication.

follow the pattern of paper, you will found that many questions are repeatedly asked every year. Identify those questions, note them separately and read about them from reference books. 

 If you don't know the answers, go to reference books and read about that concerned topic only. This way you will learn faster and effectively. 

Hope this helps.