EF lenses have a different mount and meter coupling (electronic) from FD and FL lenses. They are not compatible!
The mount issue was solved 5 years ago. There are now many different basic adaptors available with and without (macro) glass.
Since around 2006, there have also existed "AF-Confirm" adaptors. These have built-in electronic chips. As you turn the manual focus ring, they will give the "beep" and flash confirmation. They worked in Canon M and Av but not Tv mode.
Now there is a new generation of chips in the best (and more expensive) adaptors. They do all of the above, but also deal with the meter coupling Petraio Prime refers to in his comment. The ones I own work by pressing the DOF button 3 times quickly. This enters a "hack" mode, you can then electronically set the same F stop you have manually selected, using the wheel on the back and confirm by pressing the DOF button again. Now the metering works. Mr Prime, I did not believe this either, it sounded impossible. I was VERY VERY doubtful when I first heard of this, but after buying an EOS adaptor for a Summicron 35mm from
ebay seller happypagehk I discovered that, in fact, the metering automatically worked pretty near perfectly.
If you want to play with thrift-store lenses, the adaptors below will seem pricy ($50-$80). Use cheap Chinese ones instead. If you already own some great lenses with a film system and want to use on a DSLR, these are for you.
ebay seller happypagehk sells adaptors for Contax, Leica, M42, Olympus, Nikon. I have Leica and M42. His ebay shop is here
http://shop.ebay.com/happypagehk/m.html
ebay seller ml-gvalt sells EOS-FD adaptors (with glass) with a new programmable chip which work in a similar manner, I use one
items - Get great deals on AF confirm Adaprters, Peleng Fisheye Lens 8mm items on eBay Stores!
I have no link to these people, I've just used the adaptors. They are the best (at the moment). I have quite a few cheap Chinese ones I bought along the way as I experimented. Now I have a good solution to use my legacy lenses on a modern DSLR, complete with metering and AF confirmation.
This information is offered because I have been researching this over the last couple of years, I've found a very good solution, and I'm sharing it here. I do so hope it is received with the same good spirit.