Hi, i'm Tackomeil, and this is my Guide for my main champion Volibear.
I want to show you how strong Volibear Toplane can be, so without the common useless Introduction, let's get started! :)

The Relentless Storm (passive): Chosen of the Storm is one of the strongest passives in the game. It's the key for easy duelling and Teamfight-Tanking, but it has a relatively high CD and is easy countered by heal-reducing Abilities like Tristana's E Explosive Shot and the Summoner Spell Ignite.

Thundering Smash Q: Rolling Thunder gives you Movementspeed and it let's you throw your enemys behind your back. It can be used as an Escape, but it's much stronger for some pretty engages.

Frenzy (W): Is a Ult-Damage like ability, that additionally gives you Attackspeed, but has to be stacked up 3 times (similar to Jax's passive Relentless Assault which stacks 6 times). It works good with AS increasing items for faster stacking up AS. It deals 15% damage of your own health and is increased by every 1% of the enemy missing health, so you shall use it as execute(works good as kill steal/kill secure)

Sky Splitter (E): Deals AoE AP-scaling damage, that slows your enemies and fears all minions/jungle creeps expect Drake and Baron.

Stormbringer(R): A self cast Ability that gives every auto-attack a effect like Statikk Shiv. It scales really good with attackspeed and can also be used to kill low-health enemies that stand near their minions(enemy rage incomming).

Randuin's Omen: RO gives you the Armor that you need to resist the enemy toplaner's damage and the health to buff your Frenzy 's damage. The active is also nice to get away or stick on someone.

Sunfire Aegis: SC gives you good AoE damage for early Farming, since there is no real AoE like Dmg in Volibears kit excluding his Sky Splitter.

Warmog's Armor: This is your main Frenzy damage thingy. It gives you 1000 HP, which increases your Frenzy 's dmg extremely. It also increases the HP/sec from your passive The Relentless Storm

Spirit Visage: SV gives you enough MR to Sustain in Teamfights and it's passive massively increases your HP Regeneration of The Relentless Storm

Frozen Mallet: Also a main buff for your Tankyness and Dmg increase for your Bite, but helps you not letting away any enemies.

Banshee's Veil: The Spellshield is useful, but the main thing on this item is the MR and HP.

Blade of the Ruined King: This is a Strong item on Voli that gives a lot of attackspeed, a useful chasing/getaway activeand good lifesteal, but i personally don't buy it much, because i rather like to play him Fulltank with the Berserker's Greaves.

Wit's End: Gives you additional Magic Damage on your Autohits, some more MR and useful AS

Zephyr: Even more Tenacity, AS and Movespeed for your Thundering Smash

Berserker's Greaves: Gives you AS that synergys well with your Ultimate Stormbringer

Mercury's Treads: Gives you the Tenacity that you need to be useful (a stunned Bear can't run and deal damage, can he? :P)

Always take your Flash, because you can do some pretty Getaways/Catches combined with Thundering Smash.
I think Ignite is a really strong pick for duelling, but if there is no other Team Member who has Teleport or something like Twisted Fate's ult Destiny, you're the cursed Toplaner who has to take Teleport ;(

You always have to maintain your Frenzy stacks, because whenever someone tries to trade you, you can simply throw him behind with your Thundering Smash , slow him with your Sky Splitter , auto-attack a few times and bite him with Frenzy . Normally, this Sequence deals about half the Health of an enemy.

If they pushed you out, wait for the right moment when there are no enemy minions in tower range and throw your enemy in tower range with your Thundering Smash, slow him with Sky Splitter and hit him down the whole time. Normally, they get about 2 Towershots, which is imense Damage in early lvls. You should be able to kill them at this point.

If you get engaged and you think you can fight them, Activate your Ultimate Stormbringer, fear the enemy Minions and slow with your Sky Splitter and throw the Enemy in your own Minions with your Thundering Smash. Use your Frenzy for the finishing Move when it deals the most Damage, and don't be scared if you're getting pushed down under 1/3 of your health, The Relentless Storm will maintain your Health like you're a filthy Hacker.

Wait until a carry is on the frontline and pick him out with Thundering Smash. After this, you can simply stand inside the enemy team, focus on the other carrys and deal lot of damage with your Stormbringer. If you get low, don't care about it, your passive The Relentless Storm will heal about 400-500 Health/sec within 6 seconds, which is enough to deal enough damage that your team can clean up.

Volibear really is a strong toplane pick and you will have much fun playing him, but you have to get lot of experience when you can duell and when not etc.

If there are any Questions about my guide, ask without hesitation.

Enjoy Rolling through the enemy team and biting their heads of!

-Tackomeil