Singing in time with music requires a basic ability to discern the main beats of a musical composition. For some people, this talent will come naturally, others requires a more systematic approach to learning. Since each person learns in slightly different ways, the basic premise of learning to sing in time involves simple steps modified towards individual preferences. Using the method that works best for you, the ability to sing in time will come with practice and consistent effort.
Select a song that you are very familiar with and do not need music to sing appropriately. The national anthem, or a popular artist is a good place to begin.
Start your metronome at a pace that is comfortable for you to sing. Find the beat of your song and then match the tempo by adjusting the click speed, until it matches the main beat of the song.
Clap with each click of the metronome. Keep practicing until you can keep a steady tempo in time.
Tap the rhythm of the song with the metronome clicking. If you can't tap the rhythm first, you will be unable to sing in time.
Sing the song with the metronome. Keep practicing, until you can accurately sing in time. This practice may take several days, but it is only the first few songs that will be difficult. In time, you will improve your skill.