What is a one-sentence summary of the following article?
Most digital metronomes will use BPM or beats per minute as a way to measure the speed of the piece. Some mobile metronomes available for phones will even allow you to tap the beat on your screen to get the corresponding tempo.  On most quartz metronomes, the BPM is listed around the edge of the dial. Within the BPM selections, there are corresponding Italian words that are traditionally used to describe tempo, such as Allegro and Presto.  On wind-up models, you simply slide the weight up the metal bar to the desired tempo or the marking indicated on the music to be rehearsed. Many digital metronomes will allow you to set the time signature, but most wind-up metronomes do not. Time signatures consist of 2 numbers written how you would write a mathematical fraction. The top number indicates the number of beats in a measure. The bottom number indicates the value of the beat.  For example, a piece in 4/4 time would have 4 quarter notes in a measure, while a piece in 2/4 time would have 2 quarter notes in a measure. Some pieces of music may have several time signatures. To practice them with a metronome you will have to take it in parts and reset the metronome to match the changing time signatures. Setting the volume for the metronome is especially important for any digital devices. You want to find a volume that won't be drowned out by the music but isn't overwhelming either. Many swinging or wind-up metronomes will not have a volume control, but musicians can follow the swinging of the metronome to keep accurate time even if they are unable to hear the metronome over the music. Some electronic metronomes will also have an LED light that goes on and off in time with the beat.

Summary:
Set the tempo. Set the time signature. Set the volume.