One can choose to do MBA after doing their B.Tech in Metallurgy and also one can make a career shift right from the core metallurgical jobs to pursue MBA after gaining a few years of work experience.

If we consider the current scenario 80% of the students in any MBA college are from engineering background with different domains such as ECE, EEE, ME, CSE, Metallurgical Engineering, Chemical Engineering, Production Engineering, etc. Once after they step into B-School everybody gets an opportunity to learn Management subjects. 

At the time of placements, there might be a filter among the recruiters to consider people with work experience for some roles. There are also some national and international oil and gas companies like SHELL, etc which prioritize students who studied Chemical/Metallurgical/Petroleum subjects in their under graduation or students with similar work experience for the roles they offer.

In a B-School all the students who are eligible i.e who satisfy the required recruitment criteria which the company had set can take part in their recruitment and can be hired irrespective of the domain what they have chosen in Under Graduation.