5D Mk III is a Full-frame camera with speedy shutters, good for people who love sport shots. As well as it is extremely good for its sharpness in the pictures. With high ISO you can play with, without stressing how much noise control you've got to set. 5D Mk III itself have very good noise reduction
Macro is actually all about the Lens, however high-end cameras such as this, Canon Eos 7d, 1d, and other Nikon cameras such as D3 & D4 are as good for Macro Photography due to its sharpness as well.
Entry level Macro lenses are:
Nikon 40mm f/2.8 G AF-S DX Micro.
Tamron SP AF 60mm f/2 Di II LD (IF) Macro.
Sony DT 30mm f/2.8 SAM Macro.
Canon EF-S 60mm f/2.8 USM Macro.
Nikon AF-S DX Micro NIKKOR 85mm f/3.5G ED VR.
Pentax 50mm f/2.8 SMC D FA Macro.
Sigma 70 mm f/2.8 EX DG Macro.
Tamron 90mm f/2.8 SP Di USD Macro