Yes, It certainly is possible for an IIT Roorkee metallurgy student to change his branch to Mechanical.
In fact, based on recent stats, the metallurgy branch has the highest number of students opting for a branch change around 16 students out of 36 branch changers. Yet, I would like to bring to light the fact that IIT Roorkee has a bit of a complex branch change policy in comparison to other IITs.
Although branch change at IIT Roorkee might seem difficult, with the right mindset and determination one can surely get into his preferred branch.