Which moves would you choose for Metagross?
Zen Headbutt + Psychic: Great for soloing the blue man with four arms and the purple shadow with the huge grin, especially against harder charged moves that require more bulk.
Bullet Punch + Flash Cannon: Fills a small but relevant niche on gym offense as the main answer to Fairy-types.
Zen Headbutt + Flash Cannon: Powerful gym defender and flexible (albeit suboptimal) as a gym or raid attacker (unfortunately, Gardevoir also has a Psychic typing).
Of course, many players are likely to save CTMs by sticking with whatever charged move they get (or using only one for Earthquake) and then using one FTM if necessary.
(I have only 83 Beldum candy, so this is more a long-term question.)
Answers
Metal Claw + Shadow Ball.
Metagross doubly resists Psychic-type attacks. With MC+ShB it would make a great Psychic-types counter (formidable TDO and quite some DPS as well). It would also be the best counter to Gardevoir if the latter isn't using Shadow Ball. Metal Claw is good for dodging as well, pushing its TDO even higher.
There really isn't much niche for the psychic side for metagross given that we have so many options from the DPS side (even C exeggutor might give it a run for its money) and for the TDO we of course have Lugia which has absolutely disgusting TDO
On the steel side is really where it's at IMO, although there isn't much demand for steel DPS- it's always a great addition to your team of 6 (or however many you want for each type)
EDIT: Oh and FYI Metagross isn't exceptionally good for Machamp raids because steel is weak to fighting (cancels out with psychic typing). It will be slightly better for the steel variants but not the best pick for the fighting variants of machamp.
My gross is almost 3200cp now & I chose the double steel moveset purely cos I like to have a strong team for every type. He is the best steel attacker currently in the game but not the best psychic so I would go for the same. Only used once in a Jynx raid but I'm sure will see some action in future gens.