Meisters (職人, Shokunin) are warriors who fight and battle using the weapon forms of Demon Weapons, people who are able to transform into traditional weapons.
Meisters are generally individuals with exceptional wavelengths who are paired up with Weapons should both the Meister and Weapon have a compatible wavelength. This is based on the personalities of the potential Meister and Weapon. Should they be compatible, the individual would be able to utilize their chosen partner with ease. However, if one's wavelength isn't compatible, dangerous effects from the rejection can result in injury and possibly death in extreme cases.
Meisters can vary in race, even to animals such as the likes of Apes. Only Demon Weapons, most likely due to their role already as a weapon, cannot undertake the capability of becoming Meisters. The only exceptions are those who wield their family members' weapon forms due to a a special bond and the usage of Excalibur.
It seems to be a prerequisite that a Meister be physically fit. In fact, nearly all Meisters revealed appear to be physically fit. The need to be fit is given credence when Nygus noted that it's a shame that Patty is a Weapon after witnessing her take down numerous opponents without a loss in form. This is further evidenced by the fact that many of the Meisters seem to be able to run the 100m dash in under 9 seconds, with Black☆Star coming in at under 6 seconds. The real world world-record for the 100m dash is 9.58 seconds.
Types of Meisters
Utility Meister (万能職人, Bannō Shokunin): These Meisters specialize in not only resonating with different types of Demon Weapons, but also can even utilize and resonate with more then one Demon Weapon them simultaneously.
Genius Meister (天才職人, Tensai Shokunin): According to Spirit Albarn, Meister who're labelled this are able to easily master any weapon to an extent If they get even vaguely curious about their weapon form. Franken Stein is the only known Genius Meister.
Death Scythe's Meister: Death Scythe's Meisters are extremely skilled Meisters whom are known to employ the use of a Death Scythe. These Meisters are highly renown from foes alike, many of them known to be extremely dangerous and formidable, with the majority of them (sans Maka Albarn) achieving a Three-Star ranking within the DWMA.
Scythe-Meister (鎌職人, Kama Shokunin): Scythe-Meisters are Meisters who employ the usage of Demon Weapon in which are Scythes. They're perhaps one of the more powerful classifications on Meisters.
Pot Meister (壺職人, Tsubo Shokunin): A Meister whose skill is in the usage of a Demon Weapon that transforms into a "pot"; gauntlet-like gloves. Only Kilik Rung is a known Pot Meister.
Shadow Weapon Meister (暗器職人, Anki Shokunin; FUNimation "Assassin Meister"): Shadow Weapon Meisters are Meisters presumably skilled in the wielding and usage of Japanese-related weaponry.
Knife Meister (ナイフ職人, Naifu Shokunin): A Meister whom is skilled with the employment and use usage of a knife as a Demon Weapon.Sid Barrett is the only known Knife Meister thus far.
Gun-Type Meister (銃型職人, Jū-gata Shokunin): As the name implies, Gun-Type Meisters are Meisters who wield and skilled in the usage of gun-type Demon Weapons.
Sword Master (剣士, Kenshi): Sword Masters are Meister who are skilled in the employment and usage of sword-type weaponry.
Great Sword Meister (大剣職人, Daiken Shokunin): A Meister skilled in the usage of a Demon Weapon in which can transform into a great sword. Akane☆Hoshi is the only known Great Sword Meister thus far.
Lamp Meister (ランプ職人, Ranpu Shokunin): Meister who are skilled in employing weapons classified as "Lamps", including those shaped as an actual lantern or genie lamp.
Hammer Meister: Meisters in which are skilled with Demon weapons whose forms are classified as "hammers".
Axe Meister: Axe Meisters are Meisters in which employ the usage of Demon Weapons whose forms are classified as "axes".
Halberd Meister: Halberd Meisters are Meister in which are skilled in the employment of a Halberd. Depending on the Miester, they may also be skilled with the "spear" potion (making them a Spear Meister), the Axe portion (Axe Meister), or even the Scythe portion (Scythe-Meister).
Mirror Meister: A Meister that specializes in the usage of a Demon Weapon in which it's transformation is that of a Mirror. Only Enrique and Death are known Mirror Meisters.
Cannon Meister: A Meister proficient at the usage of Demon Weapon that takes the form of a cannon. Only Feodor and Death are known Cannonball Meisters.
Vajra Meister: A Meister in which is skilled in the usage of a Demon Weapon that takes the form of a Vajra. Asura is the only known Vajra Meister.
Weapons seem to be classed in the same system and rank with their meisters.
↑(Yen Press)Soul Eater NOT! Manga: Chapter 1 — Pamplet from Tsugumi: These "weapons" are actually people who can take on the forms of traditional weapons. And Meisters are the warriors who fight using these weapons.
↑Soul Eater Volume 2; Chapter 2 - Spirit:If he gets even a bit curious about another person's weapon, then he learns how to master it to a certain extent. As far as talent and skill, he's way above my wife...I mean ex-wife...Stein is a Genius Meister.