From the Alice Gallagher Clarinet Studio blog
The metronome was invented by Dietrich Nikolaus Winkel in Amsterdam in 1814. It was patented in England a few years later by Johann Maelzel, and the first composer to ever use metronome markings at the beginning of pieces was Beethoven, who started doing so in 1817.
How to Practice With Your Metronome: Basic
The first time you turn on your new metronome, you should see if you can tap your foot or clap your hands to the beat of the metronome. This may sound silly, but it is more difficult than you think if you are new to playing a musical instrument.
It is important to be able to externalize rhythm and pulse in order to internalize it. With a metronome, you can be sure that the tempo that is being set is absolutely perfect.
Being the time of year when students are busily preparing pieces for WSMA District Solo and Ensemble, everyone should be using a metronome. This blog post from Alice Gallagher does a fine job of not only teaching basic and advanced techniques for using a metronome, she also gives us a history lesson, and reasons against using a metronome. A fine post indeed.