DPJ44, 250-4 (pre 2002 NEC by your use of the dash) is a general rule, summary so to speak. This is pretty much the same (if not identicle) in other code cycles.
See 250.104 for more specifics.
Roger
[ June 28, 2005, 08:05 PM: Message edited by: roger ]
Just about anything "likely" to energize metal has electricity fed to it, and the supplying circuit will have an EGC, which is adequate to provide the necessary bonding.