Lammps is just an engine to perform MD, it's not a force field. If you have a force field that allows bond breaking and bond formation, lammps should be able to handle it. The one implementation of such force field, or rather many-body potential, is ReaxFF (but there are many others) and it is implemented in lammps. There are many examples of use of ReaxFF to model various chemical systems, so there's a chance it has been parametrized for the system you're interested in.

You can create bonds using fix bond/create: http://lammps.sandia.gov/doc/fix_bond_create.html

Within this fix, you can define the bond-type (defined with the bond style etc.) of the bond you want to create.