When you use a metronome you will develop a good sense of timing. You can use this metronome along with the beginner guitar lessons here. Farther down the page you will discover use a metronome to accompany your lessons.
You'll find a link below the bottom left of the metronome that will open a pop out that you can move about and use. If you're using a pop-up blocker the metronome window may not open until you allow popups for this website.
When using the metronome with the beginner lessons use the metronome slowly at the beginning maybe 40 beats per minute. You want to develop accuracy first not speed.
Try to strum the chord exactly when the metronome clicks, not right after. You should aim to make the click disappear.
You can also use a metronome when you are doing other things such as reading online etc. It will help to develop a steady rhythm that's essential for music.
You'll also find a free online metronome Here From Jamplay which you can bookmark for use with your lessons. Just open it in another page and continue.