kk49827 (is 49827 your zip-code, by chance??) has an excellent suggestion. If you get on the metro at Barajas airport you'll likely be one of the few (??) who get on at this "station" (true?? I really don't know, but assume this). If this is the case, do what kk49827 suggests and get yourself a space up against the wall which "butts up against" the next metro car. There will be place to stand AND room for your luggage. Beside, even though the metro ride could be long (you'll still have to change 2 or more times to get to your hotel), you'll be tired of sitting for hours on the airplane. Just "watch each others backs" when getting on/off the metro.
I wouldn't think a large suitcase would be ANY kind of target. More likely a backpack worn on the BACK. Take my advice: if it's crowded (or even if it's not), wear your backback on the FRONT of your body, straps over the shoulder, and not on your back while on the metro. Otherwise, keep a firm grip around the strap at all times and an eye on your things.
A very good friend of mine in Madrid recently had her backpack "picked" while she was wearing it on her back, either while she went into the metro, waiting for the metro, or standing in the metro car. Someone unzipped the little pouch in back of the backpack/mochilla and took out her wallet, bank book, and I.D.. She lost a good deal of money and didn't know it happened until she got home. Just be wise and be mindful and you'll be just fine.
If you have more than one suitcase each (and a backpack) I would suggest taking a taxi or contacting
AeroCITY for a cheaper (than taxi) lift to your hotel.
Good luck and let us know how you managed the metro with your bags if you do, in fact, take the metro. Thanks!
Saludos, MadridMan (have a great weekend, all!!
)