Monkey D. Luffy is a user of the Paramecia type Gomu Gomu no Mi which has turned his body into rubber. Although on the surface, this power appears to be quite average, Luffy has found unique ways to fight while making use of it. To maximize his strength output, Luffy has created "Gears" that allow him to fight to the best of his ability.
Right now, Luffy's strongest form is known as Gear Fourth, and it has been used against the likes of Doflamingo during the Dressrosa arc. Here are 10 facts that most One Piece fans don't know about Luffy's Gear Fourth.
10 Gear Fourth Soundtrack
Gear Fourth debuted during the Dressrosa arc of One Piece, in chapter 784 of the manga and episode 726 of the anime. This form was used by Luffy to finally defeat Doflamingo and free Dressrosa from his control.
Interestingly, Gear Fourth is the only form of his so far that has its own OST. Gear Second and Gear Third, which debuted earlier, weren't given a similar treatment by the anime, which makes this form special.
9 How It Works
Gear Fourth is quite an incredible power which works by Luffy using his Devil Fruit power with the maximum output of his Armament Haki. By combining the two together, he creates an armor that retains its rubbery properties and thus, makes him much stronger.
This was confirmed when he beat Doflamingo, who attacked him and was surprised by the fact that his body hadn't hardened due to Armament Haki usage. Instead, Luffy retained his rubber properties and had become an armored rubber ball.
8 Source Of Power
Every gear of Luffy's generates power by making use of a property of rubber. In the case of Gear Second, Luffy's rubber body allows him to pump blood faster and since he's rubber, he can survive the increased blood pressure without much trouble. Gear Third works by inflating his bones to turn his limbs into those of a giant and then, utilize the ability to stretch to increase the power, just like Gear Second.
Gear Fourth works slightly differently in that it doesn't rely on Luffy's ability to stretch. Instead, the power that it generates comes from compression and elasticity. Haki is used to compress his limbs and this generates an incredible amount of tension, which when released, creates collateral damage.
7 Different Haki Type
There appear to be several subtypes of Armament Haki in the story, and the one that Luffy utilizes with his Gear Fourth form is very different from his regular Haki.
While regular Haki is simply a coating of hardened armor, the Haki in Gear Fourth allows for Luffy to maintain his rubber properties. This difference is depicted by the Haki taking on tribal patterns. Katakuri, upon using Zangiri Mochi, also displayed a similar Haki pattern, as did Big Mom when she effortlessly defeated Luffy.
6 Gear Fourth Forms
Gear Fourth is the only gear of Luffy that has multiple forms. This was first hinted at when Luffy used this power against Doflamingo but called the said form "Bounceman." This gear having multiple forms was confirmed when Luffy fought Cracker and ended up defeating him using Gear Fourth: Tankman Full Version.
Against Katakuri, Luffy used Snakeman to win the fight. Gear Fourth also has the regular version of Tankman, however, that power hasn't been seen yet. So far, these are the only four known forms of this power.
5 Physical Strength
Gear Fourth is one of the most powerful forms of Luffy and in terms of physical strength, it makes him strong enough to compete with some of the elites of the One Piece world. When used against Doflamingo, he was able to do nothing to stop Luffy's barrage of attacks and was sent flying miles with just its regular attacks.
Even someone as strong as Katakuri couldn't block Luffy's Gear Fourth attacks, despite having superior Armament Haki. What's even more impressive is the fact that Luffy managed to send Kaido flying with a Kong Organ when the two fought, and although he didn't suffer any damage due to Luffy's weak Haki, the raw power was more than enough to push him back.
4 Rokushiki
Rokushiki is a power that very few characters in the One Piece world can use. Introduced by the CP-9 during the Water 7 Saga, this power is still relevant in the story and actually has users among the Straw Hats too, Luffy being one of them.
Just like with Gear Second, Gear Fourth allows Luffy to use the power to move at blinding speeds, which is similar to Soru, but that's not all. Luffy also gains the power to use Geppo, which allows him to kick the air and fly using the power of his elasticity.
3 What It Lacks
One of the biggest advantages of Luffy's Devil Fruit is that it offers an incredible range of fighting. Luffy can attack anyone as far as his limbs can stretch, however, this ability of his doesn't work as well with Gear Fourth. This is because this form of his focuses on compression rather than stretching.
The only move that allows him to launch a ranged attack in Gear Fourth is Culverin. Luffy's Snakeman, however, seems to have a much better range as most of the attacks are Culverin-based.
2 Near-Unlimited Power
Gear Fourth's power depends on how much air Luffy blows into his muscles. When using Gear Fourth, he can further inflate his body to use stronger attacks, such as the King Kong Gun. However, that certainly isn't the limit to his strength.
In One Piece: Stampede, Luffy is able to inflate Bounceman even further to a new form where he can use much stronger attacks, such as King King King Kong Gun.
1 Guardian Deity
The appearance of Luffy's Gear Fourth form is based on a Guardian Deity. This was confirmed by Oda in SBS Corner Vol. 79 and later on, by Hyougoro in One Piece Chapter 990 as well.
According to Hyougoro, Luffy resembles the Myōō in Gear Fourth state and is thus the perfect person to take down Kaido, someone who is also revered as a deity in the land of Wano. As the story progresses, fans will likely see Luffy save Wano and become the new Guardian Deity of the country.