Mad as a hatter
Mad as a march hare
Magical realism
Main chance
Make a bee-line for
Make a clean breast of it
Make a pig's ear of
Make a virtue of necessity
Make haste
Make hay while the sun shines
Make him an offer he can't refuse
Make my day
Make no bones about
Make your hair stand on end
Mal de mer
Man after my own heart - A
Man does not live by bread alone
Man who is his own lawyer has a fool for a client - A
A dog is a man's best friend
Man's inhumanity to man
Many a little makes a mickle
Many are called but few are chosen
Many happy returns
Many a true word is spoken in jest
Mare's nest
Marital aid
Market forces
Marry in haste, repent at leisure
May you live in interesting times
McCoy - The real
Mea culpa
Meat and drink
Meat and two veg.
Meet your Waterloo
Men in suits
Mend fences
Ménage à trois
Men's evil manners live in brass; their virtues we write in water
Merry Christmas
Mexican wave
Mickey Finn
Middle for diddle
Middle of the road
Might and main
(The pen is) mightier than the sword
Mighty oaks from little acorns grow
Milk of human kindness
Minced oaths
Mind your Ps and Qs
Ministering angel shall my sister be - A
Misery acquaints a man with strange bedfellows
Misquotes
Miss is as good as a mile
Moaning Minnie
Mondegreens
Montezuma's Revenge
Monty - The full
Moot point
Morbid obesity
More fool you
More honoured in the breach than in the observance
More light!
Morning person
Mother country
Motley crew
Mouth-watering
Moveable feast
Movers and shakers
Moving finger writes - The
Moving the goalposts
Much Ado about Nothing
Much of a muchness
Mud - your name is
Multitude of sins
Mumbo jumbo
Mum's the word
Murphy's Law
Music has charms to soothe the savage breast
Mutt's nuts - The
Mutt and Jeff
Mutton dressed as lamb
My bad
My better half
My cup of tea
My cup runneth over
My giddy aunt
My husband and I
My mind's eye
My old china
My old Dutch
My salad days
My stars and garters