Muse are an alternative/space rock band.
Their genre of music is reflected within their poster art work.
This helps to attract their target audience as it plays upon the futuristic nature reflecting the type of music that they produce. Muse wish to capture the attention of their already gained audience but also of those who may not have heard of them. The bright, almost garish, colours attract immediate attention to the poster the design is so 'in your face' - if this poster was A1 + in size there is no way that it can be missed.
They have managed to attract new audiences without losing the old ones - sometimes the introduction of colour isn't suited for various artists but as Muse has an energetic feel, the design sets to compliment that.
In the present day, people are looking for escapism rather than realism, this is something which is being offered by Muse's poster - the fantasy nature of the imagery offers the viewer of the poster to see a world in which they aren't used to witnessing - this may then cause a spark of interest, causing them to look further into 'Muse' - creating a larger audience for the band.