Metapod
Stats
 Shed Skin: 30% chance of recovering from status at the end of each turn. HP:
50
Atk:
20
Def:
55
SpA:
25
SpD:
25
Spe:
30

Walling Cocoon

Item: Leftovers Metapod is one of the sturdiest physical walls in the crap metagame. Iron defense boosts your outstanding defense to ridiculous levels, though it should only be used if the opponent is unlikely to switch in a counter. Bug Bite allows Metapod to hit back at the things it is walling, and String Shot can, in rare situations, allow it to force a switch on a sweeper or render it easier for the rest of your team to take out. Snore lets Metapod (sort of) absorb sleep, allowing it to hit back at least a little. Do not switch to a Relaxed nature to remedy this, as this will only make Metapod an inferior Cascoon/Silcoon. 6 EVs in speed allow Metapod to outspeed 0 Spd neutral Seedot and Lotad and hit back with a super-effective Bug Bite.
Nature: Impish
EVs: 252 HP, 252 Def, 6 Spe
Moves: - Bug Bite
- Iron Defense
- String Shot
- Snore

Other Options:

Metapod, with its almost non-existent movepool, has no other options. It learns two other moves, Harden and Tackle, both of which are outclassed by moves in the above set. Harden is simply not as good as Iron Defense, and Tackle is less powerful than Bug Bite against everything in the tier. Stick with the above set.

EVs:

As many EVs as possible should be put into Metapod's defenses, as they are the main thing it has going for it. The next thing you should focus on is speed, as this is what separates Metapod from Silcoon and Cascoon. If you want attacking power on your cocoon, go for them instead. Metapod has base 30 speed, meaning it can outspeed most of the other walls out there if necessary, and can outpace Seedot, Lotad and Sunkern that don't invest heavily with only minimal investment of its own. 44 EVs in speed will allow him to outspeed no investment Poochyena, and 84 EVs will let you outspeed 0 Spd bulky Ralts.

Counters: