Magicus Extremos: Partnership-based charm that temporarily increases the caster's spell power.
Melofors: Encases the victim's head in a pumpkin.
Meteolojinx Recanto: Causes weather effects caused by jinxes to cease.
Mimble Wimble: Ties the target's tongue in a knot, preventing them from making coherent speech, or saying incantations correctly, making it useful in duels.
(Ministry of Magic Fog): Patented charm used by the Ministry for Magic to conceal certain areas form Muggle view.
Mobiliarbus: Levitates wooden objects a few inches off of the ground and moves them in any given direction.
Mobilicorpus: Levitates and moves bodies.
Molliare: Produces an invisible cushion over the target. Is used primarily in the manufacturing of broomsticks.
(Molly Weasley's Curse): Like the Avada Kedavra curse, it kills (or freezes) the victim. It turns the body grey/blue (or paler) while it turns to stone and then another twin jinx can blast the body into pieces.
Morsmordre: Conjures the Dark Marks, which is the sign of the Death Eaters.
Mucus ad Nauseam: Gives the victim a nasty cold and an extremely runny nose that can cause the victim to collapse if it is not treated. The cold is accompanied with constant sneezing.
Muffliato: Prevents others from hearing nearby conversations by filling people's ears with an unidentifiable buzzing.
Multicorfors: Multicorfors is a charm used to change the color and style of one's clothing.
Mutatio Skullus: Mutates the victim's head, causing them to grow extra heads.

YOU ARE READING
Harry Potter spells
CasualeJust a book of Harry Potter spells if you're writing a Harry Potter book and need help with the spells. If the name of the spell has () around it than that means the spell itself doesn't have an actual name. Hope this book helps you fellow writers