High heat searing simply allows the meat to close its pores to keep all those great natural juices in the meat instead of losing the juices to the fire.
When a steak is put on the grill at a low heat, it can still purge its juices. Searing at a high heat of 350 degrees and above seals in the juices and keeps the meat juicy, not dry.
Look at most recipes for roasting. If it first suggests that you sear at a high heat, turn it down for further roasting afterwards.
Have a great day!
Mike Smollon, Co-Owner
My Butcher and More