Every time you practice your instrument when reading rhythm & counting the beats for each note in the rhythm, you should ALWAYS use the Metronome. The Metronome is a device that produces a clicking sound at a specific speed called the Tempo.
Timing is not natural, therefore, you must train your timing with the Metronome to ensure you are consistently counting and moving along with the notes in the music at the same speed. We use our foot to tap along with the Metronomes click to internalize the speed to improve our timings consistency.
Here are some Rhythmic Notes that are common for "Beginning Band" students to read, count, time and play.