If you want to see your subject larger in the frame than your current lens collection can deliver, you want a macro lens.
If you want to see your subject larger in the frame than your current lens collection can deliver, you want a macro lens. You may also want a macro lens for the excellent image quality that many of these lenses deliver. Macro lenses are very fun to use - the results from macro photography can also be very fun. And the unusually close look at these typically-small subjects is beautiful and intriguing.
While many lenses have "macro" in their names, I don't get interested in the macro feature of many of these lenses. My personal qualification for a real macro lens is a 1:1 or 1x maximum magnification ratio. This means that the subject will be rendered at life size on the camera's sensor. A 20mm subject will be rendered across 20mm of the sensor. And it will be rendered HUGE on your large monitor as 20mm is going to fill a substantial portion of the frame.
There are always subjects available for macro photography. And bringing home flowers for your wife (and to photograph of course) can even strengthen your marriage. :)
Deciding which focal length will work best for your needs is, as usual, part of the lens selection process. Longer focal length macro lenses will give you more working distance at 1:1 - this reduces the tendancy of live subjects to fly or crawl away. Longer focal length lenses also have narrower angles of view, which means that there is less background to incorporate into an attractive-looking image.