What to Include:

Genre: First, identify what you think is the artist's genre. That should be mentioned readily in the online articles you read about the artist.

Defining Genre: These are broad categories of music, such as funk, rock, metal, Christian, and so forth. For instance, when you walk into Hastings, how do you know where to find the CD that you want to buy. They are kept in bins divided by genre, such as pop vocals, instrumental, jazz, classical, alternative, etc.
Style: Then research and identify those stylistic features that appear in the artist's music that make it rap, hip hop, metal or rock. In other words, what is in the music (instruments, vocal approach, form, timbres, etc.) in an artist's music or a musical performance that go into labeling the music as rock, classical, funk, blues, and so forth.

Example: For rap, you can mention how the artist uses rhyme, or how some artists do not sing when they rap and some do. Talk about the importance of rhythm and how the artist uses it effectively. You can mention that early rap only used voice and beats (define "beats" in the genre of rap). Today, it has branched out to include the use of singing as well as other instruments. It is always very good when you can tie your artist into the history of the genre and where he fits in terms of musical style. Then listen to your artist's music and try to find places where those things are happening and mention specific examples as well as songs. Get specific! Remember that.

If your artist is a cross over artist (someone who combines one style with one or more other styles), focus on the style that you think most epitomizes the artist rather than trying to explain 3 or 4 different styles in such a short space.