Yes, you can change your branch from metallurgy to ECE after the 1st year. At IIEST Shibpur only 20% of students in each branch are given that choice except the architecture branch. There are the following conditions for changing branches:
Allocations are given on the basis of the above conditions and if there is a tie between two students then the tie is broken through the CGPA marks in physics, chemistry, and math. One who has the highest marks gets the seat.