When your opponent has no hand, and you attack his shield with horrid worm, since the worm discards a card a person draws, will the opponent be able to play the card if the shield is a shield trigger?

you don't discard the card the player draws and the player will be able to play the card if it has shield trigger. the card says, "Whenever this creature attacks, your opponent discards a card at random from his hand." that means when Horrid attacks, that is the only time the effect is activated.

bassically they discard before they take the shield.(easy lingo)

Yeah, thanks a lot

and to clear a few things out, breaking a shield makes your opponent pick it up, not draw it. This could conflict with future effects. And yes, first discard a card for horrid from your opponent, then go on to the breaking of shields.

Because the point of attack is when you "swing" with horrid worm. NOT when your opponent picks up his shield, and NOT when Horrid Worm attacks a creature. Only at the point when you declare: "Horrid Worm attack...."