Dancers who love the heavy beat of salsa music are not only feeling that, so they are also moving to the melody as the musicians play. The music touches their emotions, and it helps them know where they are within the song. Each note of the melody is part of what makes their body move, and they can work with their partner as they follow the beat together. While the love of the beat might start their feet moving, it is the emotional tones of the melody that keeps their body swaying.
Melody has often been the way musicians influence people, and emotion is usually the mechanism that responds best to it. Salsa is uplifting, and a feeling of happiness can be felt by those enjoying it. Others might say the music makes their body feel light, or they could claim it creates the sway of their hips as they dance with their partner. These are all components of the music they are hearing, and it is not necessarily a part of the beat.
Moving to music should feel natural, and the movements should be an echo the dancer feels as each note rings into their ears. Some instruments are louder than others, and they are generally the ones to carry the melody. Softer instruments can enhance it, and the beat is often the loudest of all to keep the rhythm of the dance true. It is the start of the dance for those enjoying the entertainment, but it is only one component.
Dancing to any music can feel almost like energy is entering the body, so a strong and even beat is one of the best ways to begin. Adding layers from other instruments creates the melody that will allow the dancer to feel the lighter emotions, and their body will respond naturally as the lyric line progresses.