Harry Potter Spells: The Key Spells and What They Do

The main Harry Potter spells are Expelliarmus, Expecto Patronum, Avada Kedavra and Sectumsempra, and the everyday charms Wingardium Leviosa, Lumos, Accio and Alohomora sit alongside them. The four main spells carry some of the films' most memorable moments, and a young wizard such as Harry gets his wand in the hidden London street Hagrid takes him to, before he starts at Hogwarts in Harry Potter and the Sorcerer's Stone.

What is the spell for unlocking doors? It is Alohomora, the unlocking charm. The other everyday charms are simple to place: Wingardium Leviosa makes an object float, Lumos lights the tip of a wand, and Accio summons an object to the caster. These four are small spells, which is why the big plot moments belong to the heavier magic.

What makes a spell a key one? In my opinion, it is a clear job in the plot: disarming, defending against Dementors, killing and wounding. If you are working through the saga for the first time, the Harry Potter movies in order will tell you which film to start with, and the Harry Potter movies hub lists all eleven films, including the three Fantastic Beasts spin-offs set in the same wizarding world.

Spoiler warning: the entries for the four main spells reveal plot from late in their films, so watch the film in question first.

Expelliarmus is the disarming spell, and it decides the saga's last duel. In Harry Potter and the Deathly Hallows: Part 2 (2011), directed by David Yates, Harry's disarming spell sends Voldemort's own curse back at him, and Voldemort dies as a result.

The ending then explains why the wand matters: Harry says the Elder Wand became his when he disarmed Draco Malfoy. He then chooses to destroy the wand instead of keeping it, which closes the fight over it for good.

That choice says a good deal about Harry Potter as a character. For more on the antagonist whose curse turns back on him, see Voldemort.

Expecto Patronum is the Patronus charm, the magic Harry uses to defend himself against Dementors.

In Harry Potter and the Prisoner of Azkaban (2004), directed by Alfonso Cuarón, the new teacher Remus Lupin drives a Dementor off on the train and later teaches Harry to defend himself with a Patronus charm. The film's time travel twist then reveals that the Patronus that saved Harry earlier was cast by Harry himself.

The charm returns in later films. In Harry Potter and the Order of the Phoenix, Harry casts a Patronus to save himself and his cousin Dudley when Dementors attack, which leads to the Ministry's attempt to expel him. In Harry Potter and the Deathly Hallows: Part 1, a doe Patronus leads Harry to the Sword of Gryffindor in a frozen pond.

Avada Kedavra is the killing curse, and in the films it is the weapon that finally ends Voldemort. In Harry Potter and the Deathly Hallows: Part 2, Harry's disarming spell sends Voldemort's own curse back at him, and the killing curse rebounds and kills him.

Meet the caster on the Voldemort page, and his most committed follower on the Bellatrix Lestrange page.

Sectumsempra is the spell from the Half-Blood Prince's book that Harry uses to wound Draco Malfoy badly. It comes from the borrowed potions book in Harry Potter and the Half-Blood Prince (2009), directed by David Yates.

In the film, Harry becomes convinced that Draco is plotting something and follows him, then wounds him with an unknown spell from that book. Harry became a star in Slughorn's potions class because of the Half-Blood Prince's notes, and the same book is where the spell comes from.

The Half-Blood Prince is later revealed to be Severus Snape, who also kills Dumbledore in the film, so the book connects two of the film's biggest moments. See Snape for his full arc, and Draco Malfoy for the student on the receiving end.

In my opinion, the strongest spell in the films is Avada Kedavra, and the coolest is Expecto Patronum, though no film publishes an official power ranking, so this order is my own. Here is how I would sort the four main spells.

1. Avada Kedavra. It is the killing curse, so it has to rank first on raw strength. In the final duel of Deathly Hallows: Part 2 it is Voldemort's own curse, rebounding, that ends him.

2. Expecto Patronum. Harry's use of it in Prisoner of Azkaban, Order of the Phoenix and Deathly Hallows: Part 1 shows it protecting him in three very different situations. It is also the most visually striking charm in the saga, which is why I call it the coolest.

3. Sectumsempra. The Half-Blood Prince's spell wounds Draco badly in Half-Blood Prince, which is enough to place it above the disarming spell on force alone.

4. Expelliarmus. It sits fourth on power but could be argued as the most important, because Harry's disarming spell is what turns Voldemort's curse back on him in the final duel.

The everyday charms Wingardium Leviosa, Lumos, Accio and Alohomora stay out of this order, since they are tools rather than weapons. If you want the strongest films rather than spells, the Harry Potter movies ranked page sorts the films themselves, and the Harry Potter timeline shows when each of these spells arrives in the story.