I think all of the mons on this team are really solid, the only suggestions I would really have are for the team’s role distribution. Fire, water grass is a really solid core, with a steel dragon offshoot which imo for current ou is just the more offensive variant of steel, dragon, fairy.
AV melmetal is a great fit for the team, but I would be tempted to slightly tweak the Evs to make it more specially defensive. My favourite ev spread for AV melmetal is: 128HP/ 116 Atk/ 252 Spd/ 12 Spe with a careful nature. This is just my suggestion as the team lacks any special switch ins but isn’t necessary for if you would rather have a pure offensive AV melmetal.
My main issue with this team, however is that it appears to be pure offense with a defensive pelipper for no reason. Not only does this provide anti synergy for cinderace and nidoking (although good synergy with melmetal and rillaboom) but having only one defensive mon doesn’t really add much to the team as defensive pelipper is still bodied by mons like urshifu if it tries to switch in. For this team to work I would suggest either replacing pelipper with an offensive mon, a pure screen setter or a hazards setter- or alternatively with the more specially bulky melmetal I suggested maybe replacing it with defensive tapu fini and adding one of the many ou bulky flying types as a defogger instead of probably the dragapult.
Also, if you decide to keep the dragapult I would suggest making use of its speed in the ev spread making it either fast and bulky, or fast and strong given how good it’s speed tier is past mosa ban.
Overall, if I was building this team I would replace melmetal with the ev spread I mentioned earlier, replace pelipper with this set:
Tapu Fini @ Leftovers
Ability: Misty Surge
EVs: 252 HP / 192 Def / 64 Spe
IVs: 0 Atk
- Calm Mind
- Draining Kiss
and replace dragapult with a bulky flying type such as:
Salamence @ Heavy-Duty Boots
EVs: 248 HP / 252 Def / 8 SpD
- Dual Wingbeat
(Bulky salamence is rly underrated imo and the dragon typing rly helps for this teams defensive coverage although any other bulky flying type other than moltres would work).
Even without these the team is really solid though and looks better than a lot of the teams I make.