Three Chord Songs
Basic guitar chords
When you're playing guitar songs you will find that the same chords are always used in combination with each other, and these chords are not random - they are the 1, 4 and 5 chords (or the I, IV and V chords) In the key of C, these would be C, F, G7.
For each key I've listed these three important chords, and the good news is that you can play literally hundreds of songs with just these chords. If you get interested in the theory, look up the concept of harmonised scales in my other hubs. Take a song like "Silent Night" - it's in 3/4 time, and can be played in the key of C with just C, F and G7 as accompaniment. Happy Birthday can be played with the same three chords, and it's also in 3/4 time - just count 1,2,3 1,2,3 like a waltz. Most songs are in 4/4 time, so you count 1,2,3,4 for each bar.
The vast majority of country songs can be played with four chords, virtually all Hank Williams songs for example - which might use A, D, E7, B7. Here we have the three native chords in the key of A, plus B7 - which tends to be the chord added in this style of country. Many early Dylan songs only use three or four chords. The simplicity of these songs is their strength in many ways.
Here are some suggestions for simple but great songs:
Your Cheatin' Heart
Hey Good Lookin'
You Win Again
Bad Moon Risin'
Blue Suede Shoes
Rock n' Roll Music
If you are new to guitar, the six vertical lines are the strings, the horizontal lines are the frets, so the guitar headstock would be on top of the grid picture. Try to select the right bottom note for each chord - for instance, D and D7 are just on strings 1-4, C is only strings 1-5, etc.
Guitar chords, sorted by key
In each example the V chord is a seventh chord. This is called a dominant seventh chord, and it leads you back to the I chord. So G7 to C, or B7 to E, or E7 to A, are all the same musical idea.
As this is one of the most , if not the most common, chord movements it's worth learning it well. It's good practice to memorize it in all the common keys.
Building on the basics
Let's look at the chords in C, in the last example. Every key has three major and three minor chords, plus one half-diminished chord. These are built on the notes of the major scale, which in this case goes
C D E F G A B C
This scale can be used to create melody lines or bass lines with these chords, any way you like.
Minor chords are on notes 2,3 and 6. In this key that gives us Dm, Em and Am.
So if you are playing a song in the key of C it will use 1,4,5 chords C F G7 and maybe 2,3,6 chords Dm Em Am. If you understand this it will really help in learning songs and working them out, and also in songwriting.
My other hub Guitar Lesson - chords theory covers minor chord applications.
The three major chords in different keys
Playing Blues and rock n' roll
If you use these three chords, 1,4, and 5 and convert them all to 7th chords you can play most blues and rockabilly / rock n' roll songs. The blues format is usually 12 Bars long - Chord 1 for 4 bars, chord 4 for 2 bars, chord 1 for 2 bars, then 5 chord, 4 chord,1, 5. In the key of A this would be:
A7 (x4) D7 (x2) A7 (x2) E7 D7 A7 E7
This covers most Chuck Berry songs, though they do change the order of chords frequently from the standard 12-Bar. Partly what made them so novel and inventive, and made other people steal them! Have a listen to Sweet Little Sixteen and Surfin" USA by the Beach Boys.