For perfect burgers (and buns), give them a rest.
Who hasn’t eaten a burger on a bun so saturated with meat juices that it was practically falling apart? There’s an easy way to mitigate that problem: Let your burgers rest briefly before placing them on buns. In raw meat, most of the juices are stored in individual structures called myofibrils. Cooking causes the proteins to contract and expel some of the liquid. If the meat is given a chance to rest off heat, the proteins relax, allowing some of the juices to be reabsorbed. We advocate a rest for most meat, but it’s particularly important for burgers. Burgers are always cooked directly over high heat, which raises their temperature at the surface. This in turn causes the proteins to be squeezed harder, so more moisture is lost. Letting ground beef rest is also important because a significant amount of fat will drain away instead of collecting in the bun.
For perfect burgers (and buns), let the burgers rest for 5 minutes, tented with foil and preferably on a rack so moisture doesn’t collect underneath, before transferring them to buns.