for example say there is a stock (bgm)...3,000,000 shares short...extraordinary news is delivered and we are about to resume trading...my understanding of gap up..is when the stock opens higher than previous close...the shorts are scrambling to cover their positions in the pre market trading...one on top of each other they bid...higher and higher the $$..combined with the public who have been following the story on tv, online,and news media...the $$$ continues higher...finally it opens much higher.a self fueling upward spral drives it even higher...the news is so good there are no shares for sale...the longs are waiting for the right price..and it ain't $8 an ounce...the shorts who have covered..now want to go long...the traders have entered the game..the price is driven ever higher...higher..higher..i sell some here and book cuba