WASHINGTON — President Trump has spent his first year in office breaking every rule of presidential communication, conducting policymaking and diplomacy by Twitter and eschewing the careful, subdued tones of most presidents in favor of no-holds-barred attacks on his adversaries and allies alike.

But on Tuesday, Mr. Trump will embrace the most traditional of presidential venues — appearing before a joint session of Congress for his first State of the Union address — to deliver what aides describe as an optimistic speech that will seek to reach beyond the people who voted for him in 2016.

If he sticks to the script, the president is expected to call on Congress to spend at least $1 trillion to rebuild bridges, freeways, sewers and airports. And he will use the speech to lobby millions of viewers on behalf of his plan to make a series of conservative changes to the nation’s immigration system while also granting citizenship to as many as 1.8 million young immigrants.

But if his first year has proved anything, it is that there are no guarantees when Mr. Trump faces a television camera. Cabinet meetings have veered into presidential rants. Memorial speeches have turned into self-congratulatory moments. Short photo ops have become long news conferences.