Flash is the common way to go with macro in any case.
If you are outdoor, you can do without flash but you must control light somehow: white reflective panels near the lens, that stuff. Normally one would use a flash and a reflective panel, or two flashes, because they solve two problems, motion speed and lack of sufficient light for sufficient DoF. You can do handheld macro 1:1 only if you use flash light. That will allow you to shoot insects, flowers etc. without motion blur.
If you are indoor, in a studio setup for little objects, again you probably want complete control over light. Something can be done no doubt with tripod natural light, but most will be done with flash(es). I would guess more than 90% of macro work is taken in artificial light.
I've just received today a main adapter for my big Metz. You reminded me I have yet to test it