garen mid vs Ad assassin

I actually used to play Garen mid, back in my Silver days. It's good at denying the enemy laner farm/levels/roaming opportunitues, but you lose out on a lot if you don't get ahead. There are other picks (Lulu, Ryze) that give you waveclear, good cc, and essentially do the same thing.

Garen mid is a good counter pick, yes.

Don't expect much mileage instalocking him into mid lane if you don't know what you're doing though.

Garen mid works in a very specific situation. When you're against a melee-ranged assassin. That's it. Nearly anyone else will be able to poke you all day, kite you for a month and at worst, farm under tower well to stay relevant. Come later on when your team lacks waveclear and AP burst, you'll be screwed in sieges. HOWEVER, if your enemy is also in the same boat because they're something like or the like... SURE. Go Garen mid and laugh at his attempts to kill you.

op champs are usually good