It is well known that a man is forbidden from wearing any gold because when the Prophet (sallAllaahu `alayhi wa sallam) saw a man who was wearing a gold ring, he removed it from him and tossed it onto the ground. Then he said,
يعمد أحدكم إلى جمرة من نار فيجعلها في يده
"One of you takes an ember of the Fire, and then puts it on his hand!" (Muslim no. 2090)
When the Prophet (sallAllaahu `alayhi wa sallam) left them, someone told him to pick up his ring and use it in some other way. He said, "By Allaah, I will not take a ring that the Prophet (sallAllaahu `alayhi wa sallam) threw away."
About gold and silk, the Prophet (sallAllaahu `alayhi wa sallam) said,
إن هذين حرام على ذكور أمتي حل لإناثهم
"These two are forbidden for the men of my nation, permissible for the women." (Abu Dawud no. 4057, An-Nasa'i no. 5147 and Ibn Majah no. 3595)
So it is not allowed for a man to wear any kind of gold, not a ring, nor cuff-links, nor anything else. A watch falls under this category if it is gold. If it is painted gold or is plated with a very tiny amount of gold, or it has small pieces of gold on it, then it is permissible for a man to wear it.
However, we do not recommend men to wear gold-plated watches, because people may not know that it is only gold- plated. Two things may result: first, these people may think poorly of the man who wears a gold-plated watch based on their assumption that the watch is actually made of gold. Second, people might from their mistaken assumption imitate him by wearing an actual gold watch that is either purely gold or partly gold. My advice therefore to men is not to wear gold-plated watches even though doing so is lawful. And resorting to what is clearly lawful provides more satisfaction while removing the need to wear this kind of watch.
The Prophet (sallAllaahu `alayhi wa sallam) said,
فمن اتقى الشبهات استبرأ لدينه وعرضه
"Whoever avoids doubtful matters has absolved himself (from wrong) in his religion and in his honor." (Muslim no. 2090)
However, if the plating contains a sizeable portion of gold, it is closer to being unlawful.