Rate my team - First time online

Here's my line-up. Please tell me how to improve because I've never battled competitively before.

Metagross w/Occa Berry - Lead
Ability: Clear body
Nature: Impish
-Stealth rock
-Meteor Mash
-Earthquake
-Explosion

Dragonite w/Leftovers - Physical Sweeper
Ability: Multiscale
Nature: Adamant
-Dragon Claw
-Fire Punch
-Roost
-Earthquake

Cloyster w/metronome - Tank
Ability: Skill Link
Nature:
-Shell smash
-Icicle spear
-Rock blast
-Hydro pump

Magmortar w/ - Special Sweeper
Ability: Flame Body
Nature: Modest
-Flamethrower
-Thunderbolt
-Focus Blast
-Hidden Power Grass

Venusaur w/Leftovers - Tank
Ability: Overgrow
Nature: Bold
-Sludge Bomb
-Leaf Storm
-Sleep Powder
-Synthesis

Milotic w/Leftovers - Special Wall
Ability: Cute Charm
Nature: Calm
-Ice Beam
-Aqua Ring
-Recover
-Surf

EVs would be helpful here. Anyway, I think that Dragonite could use Dragon Dance in place of Fire Punch, since EQ covers Steels already. I wouldn't call Cloyster a tank, since Shell Smash kills your defenses. I'd consider Focus Sash or White Herb as your item. There are better Fire sweepers out there than Magmortar, like Volcarona: -Quiver Dance -Bug Buzz -Fire Blast/Flame Dance -Hidden Power (Rock) Nature: Timid EVs: 252 SAtk/4 SDef/252 Spe Item: Life Orb Ability: Flame Body Milotic is better with these, since Cute Charm is too situational: -Scald -Ice Beam -Recover -Haze/Dragon Tail/Toxic Nature: Bold EVs: 252 HP/252 Def/4 SAtk Item: Leftovers Ability: Marvel Scale or -Rest -Sleep Talk -Scald -Dragon Tail Nature: Bold EVs: 252 HP/252 Def/4 SAtk Item: Leftovers Ability: Marvel Scale