Are the exposed metal parts likely to become energized? If so they would be required to be bonded by the EGC of the circuit that could energize the metal parts. If not, there is no bonding requirement.
The following is the definition of likely to become energized. Note this is in the 2023, has been in the NEC style manual for a long time, and was put into Article 100 because few people use the style manual.
Energized, Likely to Become. (Likely to Become Energized)
Conductive material that could become energized because of the failure of electrical insulation or electrical spacing. (CMP-5)