All three of these words can be rearranged to form other words (I gave partial credit to everyone who recognized that these words could be used to form anagrams), but that's not the whole story. The really remarkable common trait is that for each letter there is a word starting with that letter and using all the other letters:

STAR, TARS, ARTS, RATS
POST, OPTS, STOP,TOPS
TEA, EAT, ATE