Metz Remote System
Once you bought the first external flash unit for your camera, you start thinking about buying the next one. It's almost a rule and the reason for that is simple: one flash is usually not enough. Moving the flash off camera and using some additional off-camera flashes will give you more lighting possibilities and let you creatively use light. To control the additional flashes you could surely use some PC sync cords, but the best and most flexible way to trigger off-camera Metz flashes is to use the wireless Metz remote system. To do this, you'll need a Metz SCA 3083 (or SCA 3080 which works with mecablitz 40 MZ-... units) slave adapter for each off-camera slave flash, except for 34 CS-2, 50 MZ-5 slave and 70 MZ-5 which, according to Metz manual, do not require a slave adapter.
For a simple flash setup of two lights you can use, for example, Metz mecablitz 54 MZ-4 with SCA 3402 (if you are a Nikon user) as a master and an old yet quite powerful Metz mecablitz 40 MZ-2 with SCA 3080 as a slave. Of course, there's no reason not to have more slaves. Using two or more slave flashes would make the system more flexible, useful and comfortable as well.
The advantage of using the mecablitz 40 MZ-2 as a slave is that it's relatively cheap, so you can have two of them for the price of one 54 MZ-4. I guess you can buy one for less than $100. That way, spending less than $500, you can have quite nice wireless flash setup: one 54 MZ-4 with SCA adpater as a master and two 40 MZ-2 units with SCA 3080 as slaves. The down side to 40 MZ-2 as a slave is that modelling light function doesn't work with it.
As you surely know, in the remote mode all off-camera slave flash units are controlled by master flash and, needless to say, the whole system works without any connecting cables. There are two types of Metz remote modes: Metz cordless TTL remote mode and Metz cordless auto remote mode.
The TTL remote mode
This mode is only possible with cameras featuring TTL flash control and with the master flash units fitted with camera-specific SCA adapters. In this mode the camera settings are automatically transferred to the master which extends TTL exposure control to all the slave units.
The auto remote mode
The biggest advantage of the auto remote mode is that it can be used with almost every camera that supports standard flash synchronization (via hot shoe or the PC sync connection). In this mode the exposure is controlled by the sensor of the master flash unit. The down side to this is that the camera settings must be manually transferred to the master flash.