One of the many questions around wine etiquette; When a guest brings wine is the host obligated to serve this wine; the quick answer is no.The host has prepared the meal and may have specific wines in mind to compliment it. The act of bringing a wine is more of a house warming gift for the host to enjoy when they wish. However, if it is agreed prior that the guest will bring wine for the dinner the wine then that wine should be served
Myka Meier, founder of Beaumont Etiquette, weighs in: “When someone brings you a bottle of wine, you as the host are not obligated to open or serve the bottle that you have been given. It’s completely at the host’s discretion, and if you were just given a bottle that you’d like to open and share, then you may do that or store it away for a rainy day!” So there you have it. Unless the guest and you specifically mention bringing "the wine for dinner".
Guests, using the boarder-house reach to fill up your glass and others is a definite faux pas. Allow your host to fill your glass, even if you have to ask for ‘another taste of that excellent wine.’
"When someone is kind enough to extend an invitation, you should be kind enough to bring along a hostess gift," says etiquette expert Jodi Smith of Mannersmith Etiquette Consulting. "My mother taught me to never arrive at a party empty handed," says interior designer Maggie Griffin.
Keep in mind that this is a gift, not a side dish to be served with the dinner. If the host would like you to bring a dish to share, she/he will ask you to do so when you accept the invite
To help make your point that a bottle of wine is intended as a gift, hand it to the host and say something like, "Thank you for having me! I hope you can enjoy this soon." This gesture relieves pressure on the host when deciding whether you were hoping to enjoy the wine that evening or not. It also helps to present the bottle of wine as a gift, wrapped in a wine bag or even with a simple bow and "thank you" note.
Your main priority as a host is to make your guests feel at ease from the moment they step into your home. If your guest shows up with a bottle of wine and doesn't offer any instructions, it's best to say thank you and then ask if they would like you to serve it with dinner. This way, your guest has an opportunity to confirm that it is a hostess gift and that the wine, at your discretion, can either be opened that evening or stowed away as you please.
If the wine is to a gift it is always best to wrap the wine or use a fancy wine bag.
Being a Perfect Host
Guests are not often aware of proper wine etiquette and may surprise you by requesting you serve a red or white when the meal selection suggests otherwise. Or they may request to try the wine they brought; be the perfect host and honour their request.
When heading over to your host’s home with a partner, you should always bring at least two bottles especially if there will be other guests. However, if you and your partner are not big drinkers, it is more than OK to bring one bottle of wine, and then an additional gesture such as a bouquet of flowers, or something sweet for dessert.*1
If the bottle of wine you bring is not opened or not finished can you take it home with you? NO! If you had expected it to be opened you should have let the host know it was a contribution to the meal according to etiquette experts.
The longer the friendship the more likely these etiquette rules will be relaxed.
*1 - Myka Meier, founder of Beaumont Etiquette