All I Want For Christmas Is You by Lady A is in Bb at 140 beats per minute and runs 2:38 across 52 bars. It uses 14 chords — F, Gm7, Bb, Bbm, A7, Dm7, D7, Bbm6, and a few more. The chord diagram changes as the song plays and the words light up as they are sung, so you can strum and sing along without reading ahead.
Want the melody line note by note? All I Want For Christmas Is You guitar melody tab.