Yes the metro line is closed. There are substitute buses but I wouldn't bother with that. The taxi has a fixed fare of 30 euros each way from/to the airport, from or to anywhere in the city centre. That's anywhere within the M30 ringroad which is probably all of what you want.
If you go direct from airport to the stadium, the Wanda is outaide the M30 limit so they probably put the clock on. Either way it may be around the 30-40 euros mark but i dont know exactly. its very close to the airport.
There's also an Airport Express bus (5euros) for anyone alone or on a budget which stops at a few designated places and ends at Plaza Colon, pretty central. Course if you then need a taxi you'll end up saving a couple of euros. Get a taxi.
Good luck everyone and any questions about Madrid drop me a pm
Edit I now realise you mean Barajas the town. I still think taxis are the best idea. You could get one to a metro station like Hortaleza and then the metro. Depends if you're going to do anymore travelling in Madrid. You'd have to pay for the card and then load the journeys on. Lot of faffing unless you're going to use it a few times.