Depends on the meat, weight and the cut - I always put foil over the meat and then a clean tea towel, the reason being that if the tea towel has picked up washing powder that taste can transfer.
Folk have a misconception about resting - they do not realise that the meat carries on cooking after it has been taken out of the oven.
My general rules are a minimum of 20 minutes for say a leg of lamb, reasonable beef joint (maybe 30 mins on giveup's rib if there are three ribs to it), pork and chicken. Turkey 18 to 25lb, 40 mins, otherwise 20-30. Venison/game 10 mins....
I even rest fish and scallops for a few minutes (and usually there is a sauce etc to finish off so it is a natural thing to do).
It is one of the most important things that separates a good cook from an average one.