I'm so confused! What's the bar? How do I fit the strum into it?

Getting the strumming right is the most important thing in the first place. Most students I encounter are a bit over-confident about the quality of their strumming.

  • Can you strum and do changes without looking at your guitar?
  • Can you strum an a patter, do timely changes and in the meantime whatch the footage taken in the cockpit of a train? (example: https://www.youtube.com/watch?v=v0vrhCqFUFE )
  • Have you tried 16th note strumming and are your changes still solid without losing track of the drum beat or metronome?

yes? Than you can be confident you’re ready to start singing.
If the things above make you stutter, miss chords or lose timing too much, you need to reinforce those fundaments a little more

To help you with that, this post could help you as well; it’s about getting that rhythm playing to solid automatism so you have more “processor power” to allocate to the singing part.

Hello Henry.
Welcome to JustinGuitar and the Community.

Most songs you learn to start are in 4/4 time.
Four beats per bar.
Four Downs.
Four corresponding Ups.

Love Me Do
First two lines: (A over 1st Love, D over “do”)
A D
Love, Love me do,
A D
I’ll always be true,
Where are the bars? The recommended strum pattern in the beginner book is:
D DUD D

Four Down strums in the pattern so it is counted as:
1 2 & 3 4
Down strums are on the beta, on the numbered count. Up strums are &.

See if this helps.

You need to pay more attention to the drum, the bass, the instruments and less attention to the singing. Singers have the freedom to sing their melodies across the start and end of bars, to begin singing before the 1, the finish singing after the 4.
The foundation of the music is the solid rhythm keeping regular time and the singer does not hold the clues you need to be listening for.

I only wish someone had told me exactly this before I started playing guitar, especially the last sentence.

try to train your ear to listen only to the instruments , forget the singer
with a bit of training you can hear the instruments separetly

you can do that on every song you listen to ( try songs played by a band with drums and bass etc )