By sitting on huge reinforced concrete pylons? By the metal parts touching?
Or are you referring to bonding the various components together? (probably) Is that even necessary? (probably not) Look at the direction for dealing with building/structural steel. (Or give us a lot more information about the question.)
You won't find anything in NEC about lightning protection, but check out NFPA 780. There are also more than a few web sites about it. (Or start a new topic asking specifically about lightning protection for a bridge.)