Klinklang

KlinKLANG... KlinKLANG... KlinKLANG...

...that's the sound of a Pokemon being buried under the weight of many, many better Pokemon. Klinklang didn't have much going for it from the start; low stats combined with the fact that it's a Steel type, which is not only a "meh" attacking type, but a type that meant that Klinklang was destined to go head-to-head with Metagross, one of the titans of the meta.

Best PvE Offensive Moveset

• Metal Sound and Flash Cannon are the best hope that Klinklang has, though it's not good at using them.
• Thunder Shock and Zap Cannon can work for Electric damage, though they generally shouldn't.
• Charge Beam, Hyper Beam, and Flash Cannon are just bad.

Best PvE Defensive Moveset

• Charge Beam is the better Fast move due to higher base power and energy gains, allowing it to out-pace Thundershock and Metal Sound.
• Flash Cannon or Zap Cannon are going to be Klang's best choices, with each holding advantages and disadvantages.
• Hyper Beam is the inferior choice on defense.

Thunder Shock is preferred over Charge Beam for its faster energy gains. 

Mirror Shot is recommended for its low energy cost, which enables it to bait shields. Flash Cannon isn't particularly valuable due to Steel-type moves not being very relevant in the meta, but it does get STAB and can hit decently hard in in neutral fights. Zap Cannon is a bit ambitious due to its insane 80 energy cost, but isn't unreasonable due to very high energy generation from Thunder Shock.