Main, 21, joined the club on an initial 28-day loan and is open to staying longer.
"I've come out to get some experience and play a lot more games and up my fitness," he told Shrewsbury's official website.
"Hopefully I'll score a few goals and then at the end of the month I don't know, we'll see what happens.
"Whether it gets extended or Middlesbrough want me back, I'll just take it as it comes."
Main started his career at Darlington before joining Boro in 2011.