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Are you doing this to pass inspection, or just because you read about it and thought it sounded important to do? If you need to pass inspection, you should talk to your inspector in advance and see what they think.
The pool frame can be bonded, though sometimes it is more difficult than other times. The rule is that every metal piece 4" or larger must be connected to the bonding wire. Often the existing bolted connections between the frame pieces are sufficient to complete the circuit, but if they are not you are supposed to run a wire to each independent piece.
The bonding wire connects the water and everything else conductive that a person in the water could possibly touch or which could conduct electricity into the water, and makes sure they are all at the same electrical potential. In an ideal world it would never carry any current. But in practice there are places where there are stray ground currents that are present most or all of the time (normally because of electric company infrastructure), and the bonding system will carry those currents around the pool.