Bronzong

Without the stalling and support moves of the main games, the big metal bell is left without many purposes. Its attack is too low to have any offensive presumption (using it in a Machamp raid would be as effective as using a Jolteon or a Golduck), and its defensive capabilities don’t really stand out either.

Best PvE Offensive Moveset

• Confusion and Metal Sound have STAB and are overall superior to Feint Attack.
• Heavy Slam is the best of Bronzong’s charged moves, with Flash Cannon as a strictly inferior version.
• Psychic can be paired with Confusion for Psychic-type damage.
• Payback doesn't have any use; better to consider Dark-type Pokemon instead. 

Best PvE Defensive Moveset

• Confusion is of the best fast moves for gym defending.

• Heavy Slam is the only 2-bar charged move option.

• No reason to use Flash Cannon over Heavy Slam.

• Psychic is hard to dodge and might punish Fighting-type attackers even more. Psyshock is a 3-bar alternative

• Payback takes too long to access as a 1-bar move. 
• Feint Attack and Metal Sound fall behind.

Confusion takes advantage of STAB to significantly out-damage Feint Attack, though the latter could be used in very niche cases. 

The July 2019 move rebalance update gave Bronzong the addition of Psyshock, which is now its cheapest charge move energy-wise. While additional Psychic-type damage might be a bit redundant due to the high damage output from Confusion, the unspectacular energy generation makes low energy charge moves much needed in order to apply shield pressure.

Payback is the preferred secondary Charged Attack; it deals overall good damage and punishes Ghost- and Psychic-type Pokemon. Bulldoze can be used to hit opposing Steel- Pokemon super effectively, but it's an underwhelming move. Both Flash Cannon and Heavy Slam are fairly underwhelming despite receiving STAB.

Great League: 3.5 / 5

Bronzong is a solid Pokemon in every sense of the term. It has good typing, good stats, and a good moveset, which combine to make it a very powerful Pokémon in its own right. Bronzong's laundry list of resistances allows it to come in on some otherwise threatening Pokemon, and its good stat distribution and move options let it beat down Pokemon that would otherwise threaten its team. Playing Bronzong to its strengths and making sure that other team-members need those strengths are the keys to success with Bronzong. Just make sure that its weaknesses are covered too! 

Ultra League: 4 / 5

The level 50 update provides an enormous performance boost for Bronzong in Ultra League, enabling it to reach the 2500 CP cap and increasing its stats and wins across various matchups. The abundance of resistances from the Steel typing with Psychic typing to negate the weakness to Fighting-types is a great combination for Bronzong. Losses against Giratina and Registeel suggests Bronzong to favor playing in the Premier Cup rather than open Ultra League. 

Master League: 0 / 5

Bronzong has no real utility in the Master League.