Loop packs are a great fit for producers looking for melodies, chords, chord progressions. They're also helpful when you need background music that's not too busy and doesn't distract from the vocals.
A loop pack is an audio product that features loops of synths & drum beats set at various tempos to give producers a good idea of how these sounds will work with different types of music in question. The first thing on most loop packs is some sort of intro or melody - usually with slow-to-medium tempo drums. These melodic loops can be really useful if you're writing vocal songs but find it difficult to come up with catchy melodies on your own due to writer's block or whatever other reason one may have.