I want to run an MD simulation using gromacs for metal ion bound protein. I need to know the parameters as well as the force-field used for this kind of simulation.
You can use the MCPB.py tool (DOI:10.1021/acs.jcim.5b00674), which allows you to parametrize a metalloprotein using AMBER force fields. You have to do some QM calculations that will be used as inputs by the MCPB.py tool. The tool gives you the topology files for the AMBER software and you can convert them using ACPYPE software to have a topology compatible with GROMACS. Check this tutorial (http://ambermd.org/tutorials/advanced/tutorial20/mcpbpy.htm)