F- Flurry
SW- Sonic Wave
RS- Resonating Strike
S- Safeguard
IW- Iron Will
T- Tempest
C- Cripple
DR- Dragon's Rage

Lee Sin is hard to master, but upon mastery is almost unstoppable. He is a great solo champ if played correctly, and requires aggressiveness and smart decisions to play.

Pros
-Good 1v1 champ
-Tanky dps
-Has amazing burst

Cons
-Missing a SW will be very costly a lot of the time
-CC can cause to miss RS/IW/C

I use full armpen runes which is very beneficial early game due to the boost in damage.
Having full dodge runes makes Lee superior to other AD melee based champs.
The CDR can either save your life while running with no hp, or get off that last SW to finish off your opponent.

I highly prefer lane Lee. Laning with Lee Sin allows you to max your SW and in turn do a lot more damage. Also, Lee needs A LOT of farming in order to get his whole build. You will be more of a use to your team as a farmed lane Lee than a Jungle Lee.

Having 21 in offense is overall great for Lee Sin due to getting the CDR, armpen, and crit dmg as well as having an upgraded Exhaust. 9 in defense allows Lee to reach 9% dodge and have increased MR.

Doran's Ring- This item gives Lee a nice boost beginning game to enable an easier first kill with the survivability and damage.

The Brutalizer- Getting this beginning game basically means that Lee does true damage. Lee's SW/RS and DR both deal physical damage so this scales with the armpen and makes them very powerful with this item. With the armpen runs and this you have 46 armpen. This makes most champs beginning game have zero armor and very vulnerable so just make sure to farm quickly beginning game to get this.

Merc Treads- This is always a better choice than Berserker's Greaves. The extra attack speed isn't needed with F. The MR and tenacity help more due to survivability.

The Bloodthirster- 100 dmg? yessir i want. As long as you farm enough and avoid dying this item is amazing. The lifesteal makes it so you can leave a fight with no hp, go kill a group of minions with S/IW and join the fight again with full hp. Its a nice item for Lee Sin overall.

Warmog's Armor- This is where you start to become more tanky. The huge amount of hp makes it so you can tank in team fights with S/IW on and get health back while your team kills the enemy.

Atma's Impaler- A necessary item along with Warmogs to give Lee more damage.

Youmuu's Ghostblade- Good for chasing and the armpen is nice as well. Also the faster attack speed helps with lifesteal.

Trinity Force- This item ends the build nicely with all the different things it gives, the crit is very helpful to Sin. Just an overall good item for Lee.

Force of Nature- 76 MR = awesome decide whether you need this or not in game, Lee is quite tanky with the Warmogs and Trinity Force, but this is a nice item to get. Also decide when to get it. Getting it last inst always best. Most games you wont see your last item.

Lee's build takes a huge amount of gold to acquire all of it, so getting a HoG or Avarice Blade (since it is needed to make Youmuu's anyway) may be a good investment sometime early game to help late game.

Exhaust- Great for 1v1, slowing down enemies, or taking an enemy out of team fights for a couple seconds.

Flash- Basically essential for all champs. nuff said

Ignite- A good alternative to exhaust for more dmg.

Ghost- I prefer flash, but if ghost is how you play, use it.

Any other summoner's spells are useless for lee unless you are jungling with smite.

Flurry- The attack speed is good, and if you learn how to use your spells correctly you will last longer with energy in fights too.

Sonic Wave/ Resonating Strike- Lee Sin's main move, can be used to initiate fights, or search for nearby invisible champs. Hitting this skill shot is needed because its damage is good as well as the kick to the opponent.

Safeguard/ Iron Will- Maxing out this second is needed for the extra lifesteal/ spell vamp. Jumping to wards/champs can save your life, save your friends life, or help kill enemies. Also if you are leaving with no health and an ignite on you this will save your life.

Tempest/ Cripple- Good aoe if you hit a lot of champs in a team fight with the slow and reduces attack speed. Also good against champs like Jax whos damage scales with attack speed. Can be used to get away or catch up to champs as well.

Dragon's Rage- A great damaging ulti, very useful in many different situations. Best to be used on more than one champ to knock up and deal dmg. My favorite move with this is to put SW on the enemy, and, after using DR, use RS to deal a massive amount of dmg with RS dealing 10% of the enemies' missing hp. DR can also be used after flashing in front of your enemy and kicking them back into your allies. Lastly can be used to escape, while running kick the enemy back and maybe throw in a T/C beforehand if you can afford it.

Lee Sin is a powerful champion when used correctly. Thanks for reading my guide and don't forget to vote on it!