The Harmonica Store

I wanted to get a blues harp to play with some blues songs on my guitar. Today I went to a music store and I guy sold me the key I wanted, the harmonica is a 'hot metal (horner)'. I played it with some blues riffs in the key of the harmonica, but the harmonica didnt mesh well with my blues sound... are blues harps different from regular harmonicas?
my harmonica is in G, so what key in blues do I play on my guitar

The G harp works well with the Blues played in the key of D.
If you play the harmonica in the key that it is labeled, you are playing straight harp or first position. You would be using mostly blow notes. This is the position that most of the "folk" type music is played , as well as being best suited for playing melody lines. To play cross harp (second position) you are playing the harmonica in a key other than the key in which the harmonica is labeled. The main reason for doing this is that the draw notes can be bent for more expression and to get your "blue" notes (flatted third, fifth, and seventh) which are not naturally present on the harmonica for the key in which it is labeled. This is the position that is mostly used for blues, rock, and country. In these styles the harmonica is usually not playing the melody, but is used to add fills and riffs that compliment and add to the music. To find the key of the harmonica to play cross harp, count up a 4th from the original key. So using this example, and depending on the style of music being played, if the song is in the key of D, you could play a D harp in first position, or a G harp in second position and both would "sound right" with the music. Of course the G harp could be made to sound more "bluesy" than the D, and would work better on blues, etc.