Hello! My username here on mobafire as well as League of Legends is Nullatrum as you can tell. This is my very first guide, and I hope it can be a good one. I am not trying to go for the "Best Jayce Guide NA that will get you to Challenger I and win every LCS" because first of all, I do not possess that ability. At the current moment I am only in Bronze Division III so I don't have many credentials, but this guide is pretty similar to most guides out there with slight variations in accordance to my play style.

Jayce, the Defender of Tomorrow, is a Bruiser/Figher AD primarily Top-laner champion with one aspect that puts him above a lot of top-laners: he is ranged. The way Jayce works, if you are new to him, is that he has two forms: hammer and cannon. He switches between them by using his ultimate ability "Mercury Cannon/Hammer".

His Cannon form allows him to become a ranged champion whose auto-attacks shoot out blue-looking energy balls from a distance, and whose abilities include firing a larger skillshot, an energy gate that allows increased movement speed and when shooting his skillshot through it will speed it up and allow increased damage, and an ability that increases his Attack Speed by a lot for three autoattacks. In his cannon form, he has a move that allows him to "dunk" on other champions/minions, a Lightning Field that adds DOT to an enemy champion/minion, and a Thundering Blow which knocks back an enemy and does substantial damage.

Jayce can be a huge harass in laning phase, as many to laners have poor range and Jayce can simply autoattack them to harass them and gain CS in the process of making them back off. He also is a great initiator and in proper hands without going against an overfed champion, can 1v1 a large majority of champions, especially late game when he does practically as much damage as an ADC.