The second team in the Spanish capital, Atletico have enjoyed considerable improvement in their fortunes since former midfielder Diego Simeone took over as coach in December.
They defeated Unai Emery's Valencia 4-2 at home in the semi-final first leg last week.
Valencia are seven points above Atletico in La Liga and on course for Champions League qualification, demonstrating the extent of the achievement if Simeone's players do progress past the third-ranked team in Spain.
Despite their two-goal aggregate lead, advancing to the final is no formality for Atletico. Valencia remain a dangerous prospect and have the advantage of two away goals prior to the return fixture at Estadio Mestalla on Thursday.
Emery's side defeated Real Betis 4-0 in their last outing on Sunday, while Atletico saw off Espanyol 3-1 at home.
In the other semi, Sporting Lisbon of Portugal hold a 2-1 lead going into their second leg away to Athletic Bilbao.
Following the arrival of Marcelo Bielsa as coach, fresh from his stint in charge of Chile, Athletic have been one of the success stories of the European season.
Playing a high-tempo, pressing game, they defeated English Premier League champions Manchester United 5-3 on aggregate in the round of 16, before seeing off Bundesliga side Schalke 6-4 in the quarter-finals.
Athletic are sixth in La Liga, and on course to earn a place in the Europa League again next season.
They led Sporting 1-0 in the first leg last week, but conceded twice in the last 14 minutes to cast serious doubt over their progression to the final.
Sporting have underwhelmed in Liga Sagres this term, and sit 13 points back from leaders Porto in fourth place.
But they overcame English Premier League title contenders Manchester City in the round of 16, going through on away goals following a 3-3 aggregate draw.
And Ukrainian outfit Metalist Kharkiv were dispatched 3-2 over two legs of the semi-finals.
Sporting have stated their credentials to become the third Portuguese team to reach the final in the last two seasons, following Porto's victory over Braga last year.
It will be up to Bielsa's Athletic to stop them if we are to see two Spanish clubs fight for the trophy at the Arena Nationala, Bucharest, next month.