Loving a child doesn't mean
giving in to all his whims;
to love him is to
bring out the best in him,
to teach him to love what is difficult.
-Nadia Boulanger
The very best metronome is the one you incorporate into your body and mind, through either practice or an inborn sense of rhythm. I call this your inner metronome. It is the one to strive to ultimately own.
From an early age, I have my students use metromones. They use them on simple quarternote rhythms(1 tick per note). Then I teach them to allow 2 beats per note. Over the many years of teaching only a few children who came to study violin with me had an inborn sense of rhythm.
Most need help and direction to find their inner metronome.
The metronome, produces a set of number of clicks per minute. If it is set, for example at 60, the metronome will give 60 clicks
per minute. Each click representing a beat. The letters M.M. stand for MAELZEL'S METRONOME. John Maelzel invented the metronome in 1815 for measuring the time or duration of notes by means of a graduated scale and pendulum, which may be shortened or lengthened. The newer electronic/ battery metronomes are superior to Maelzel's. They are more accurate and easier to use, many are more portable.
Tempo is an Italian word used to express the speed at which a composition is executed. Many of the terms used in the interpretation of expression of music come from the Italians, who were the first to make wide use of them.
Prior to 1600 tempo marks were almost unknown.
On music you might see
M.M. = 60
M.M. = 60
M.M. = 60
In slow tempos of compound meter such a s 6/8 - 9/8 - 12/8 the composer uses the eigth note in his metronomic markings, and in fast tempos the dotted quarter
M.M. = 72
M.M. = 72
By this means a composer can precisely indicate the rate of speed he wishes his composition to move.
Suggested tempos and markings
largo 40-60
larghetto 60-66
adagio 66-76
andante 76-108
moderato 108-120
allegro 120-168
presto 168-200
prestissimo 200-208
Metronomes I own
Seth Thomas Wood pendulum type windup(pretty, not really reliable)
Tempus Quartz QM-30 (use the most, with the students)
Exacto Quartz (daughter's)
Seiko Digital (my preference when practicing)
Seiko Digital clipon (kept on music stand)
Hallmark tree ornament - the mouse on the metronome, does click(gift)
Books
Metronome Techniques by Frederick Franz - New Haven Connecticut
Before a student even begins trying to use a metronome with a solo, I recommend he/she use an etude that has a very simple rhythm and practice playing along while reading it.
I also recommend you use the smallest increment of note value, and the most populous one in the etude,,, in the beginning,, I do not mean using a 32nd note, but eighth or quarter notes are good.
You need to decide before you play what type of note would be best to use in the piece you are working on for the note the beat will be beating with. Some pieces are best using the eighth note and some the quarter note.
One tip is...you can never catch up with a metronome.....So when you get off the beat with it, stop and begin again, not back to the beginning of the piece, but from a place near when you stopped.
If a student is having a great deal of trouble missing where the beat falls as he/she reads the music, use a PENCIL, and put a line/slash mark under each beat. Sometimes it will fall on a note, some times on a dot, sometimes on a rest.
You should see the first movement of the first Bach Sonata no. 1 in g minor in my book. I had to subdivide it to count it correctly,,lots of pencil slashes..........to stay with the metronome.
A metronome can become your best music study friend. At least that is what I tell my students.
METRONOME 
= 60
= 60
= 60
= 72
Books
.....to stay with the metronome.