The 20-year-old, who has played only 16 first-class matches, will become the third new spinner to debut for England in the space of four Tests.
"He's full of confidence, he has a lot of energy and he's very switched on," captain Joe Root told BBC Sport.
"I've been very impressed so far and I'm looking forward to seeing him in action."
Bess, who has played for England Lions and made a century for MCC against county champions Essex in March, gets his opportunity after Somerset team-mate Jack Leach suffered a broken thumb.
Leach made his England bow in the second Test on the tour of New Zealand, two matches after Mason Crane debuted against Australia in Sydney.
"Dom knows what he wants to do and how he wants to go about his business," added Root. "He has a good idea of his own game.
"It's a great opportunity for him. He seems to have an
Bess' inclusion means that England will choose between pace bowlers Mark Wood and Chris Woakes for the final place in their XI.
That continued an awful run of away
In contrast, and in the same time period, England
Root, entering his second summer as Test captain, said: "We've had different challenges to deal with. We weren't at our best over the winter, so this summer is a really good marker for us.
"More than anything, we want to see a few lads grow and to give ourselves the chance to be consistent over a long period of time, to be more successful everywhere we play, not just at home.
"When we do play in England, we want to be more consistent in back-to-back games. That is something we have struggled
As well as handing a debut to Bess, England have recalled Jos Buttler to bat at number seven, despite the Lancashire wicketkeeper having played only four first-class matches since the end of 2016.
Buttler, who has made three of England's five fastest one-day international hundreds, arrives from the Indian Premier League, where he hit a record-equalling five consecutive half-centuries.
"He's in a really good place with his game," said Root. "It's like he's making his debut.
"All I want him to do is be the best version of himself. In 50-over cricket, some of the best hundreds he has made have been when he has come in after 25 overs and he has had to think about maximising the team's score. He has done that on a number of occasions.
"If he can get in the mindset of playing the situation and trust his natural instincts, he'll get the best out of himself and we'll see some great things from him. It's an exciting selection and it's a great opportunity for him."
The skipper had previously stated that it was his preference to bat at number
"I see this as a long-term thing," said the 27-year-old. "I want to pick the best side and do what gives us the best chance of winning.
"When I started as captain, I wanted to make sure I could separate the two. When I was on the field I could focus on that, then get my head around batting. Now I have a bit more experience, I feel I'll be able to do that from number three. I feel that is the best place for me to bat."
Root's predecessor, Alastair Cook, will equal the record of Australia great Allan Border by playing in his 153rd consecutive Test.
Cook, 33, has passed 50 only once in his past 17 Test innings - albeit that was an unbeaten 244 in the fourth Ashes Test in Melbourne.
"He's hitting the ball well in practice and he's got a couple of good scores in county cricket," said Root.
"The record is an unbelievable achievement. He seems to continue to break records, which is phenomenal.
"He knows what he needs to do to score runs and he has some great memories of this ground.
Pakistan won on their last visit to Lord's and famously celebrated with press-ups on the outfield.
The 2-2 series draw in 2016 took them to the top of the world Test rankings, but they have since dropped to seventh, two places below England.
Experienced batsmen Misbah-ul-Haq and Younis Khan have retired, while leg-spinner Yasir Shah is injured.
Shadab Khan, a 19-year-old leg-spinning all-rounder, is set to play, while opener Imam-ul-Haq, nephew of former batsman Inzamam, made his debut against Ireland.
"The last four months have not been good for the England team," said Pakistan captain Sarfraz Ahmed. "They have not had a good time.
"As a captain, I see England having less confidence. We have some talented young players and we will try our best to perform well here."