Can I attach a leica m lens to any digital camera?

If the lens is a screw-mount as were most all older Leica lenses you should be able to find an adapter for M-mount to Canon, Nikon, Sony (aka Minolta MAXXUM mount), Pentax DSLR cameras.

If the lens is a Leica bayonet-style mount like they used on their R-series SLR cameras it may be more difficult to find adapters.

Curious as to why this is something you'd want to do since you'll lose auto metering and auto focus.