I like them because they are good finisher moves. But I'd skip them and devote all my energy to compound moves for the chest if i'm going for purely mass...
I used to do flies all the time to try and get that center cut between my pecs, but I found that heavier dumbell weights seemed to tire my arms long before my chest really did.
Since then I've found that doing concentrated heavy close grip bench presses gives me much better definition between my pecs while also building mass.
I've started doing these again in one of my chest workouts a week.....my chest is a lagging bodypart right now.
hadn't done them in a long time.
one thing I like to do is turn the outside of my fists in at the end of the movement (so that my palms are facing me)....gives a good squeeze in the middle of your chest.
flies are good for your chest more than just one way.
they work the midle of your chest and they also stretch your chest making more room for mass.
i do flat bench,incline bench superset w/incline flies and then
finish off with decline,but i do chest once every week and a half
i've noticed some nice gains
I use a fly machine which simulates a hugging motion. As far as I know, the chest muscles can only do two things: press and hug. So I do at least one exercise to cover each of these actions. Seems to work pretty well...