If you want to get closer to your subject and pick up the finer detail then macro lenses will give you the edge, allowing you to take close-up shots with extreme detail. The unique advantage of the macro lens is that they allow you to magnify the subject so that it appears from 0.5x life-size or ideally 1.0x life-size or greater, on the camera sensor.
When you want to capture a close-up shot of a nervous animal or insect and pick up the finer details, you want to do so without disturbing the subject. A lens with a longer focal length, from 100mm to 180mm, will ensure that you have enough working distance between you and your subject not to disturb it or the light around it.
Focal length for macro isn't always about getting closer to your subject. A higher focal length (i.e. higher number) enables you to have the same magnification ratio whilst being able to stand further away. For example, using a 180mm lens to capture butterflies gives you the distance you need so as not to disturb your subject, whilst still retaining the macro magnification.
As you increase your focal length, your working distance will also increase, so you will still be able to achieve the same magnification ratio. Your working distance is the distance from your subject to your focal plane.
The diagram on the right shows the distance from the end of the lens to the subject.
Longer focal lengths in the macro lens genre may cause higher levels of camera shake making it harder to capture a sharp, crisp image. The Image Stabilizer in the lens helps to eliminate most hand-held camera shake, if you select a lens without IS you can use a tripod to stabilise the camera and lens but your camera and lens are not as easy to move around.
The right lighting set-up will allow you to use a higher shutter speed, giving you crisp shots of moving objects. Canon's Macro Ring Lite MR-14EX Il and Twin Lite MT-24EX provide specialised lighting systems, that help to illuminate your subject, either with more even light, as with the Ring Lite or more directional light, for texture, with the Twin Lite. While the EF-M 28mm f/3.5 Macro IS STM comes with two built-in, controllable, LED (Macro Lite) to provide extra illumination and eliminate shadows cast.