adaminnh, well, you know what they tell you, from the time you're a little kid in grade school, right?: Whenever you find yourself in a disagreement like this, the way to resolve conflict is you "talk about it" with the person. Right? Sounds so simple, and who can argue with "talking about it", right? It just "rolls off the tongue". But as I'm sure you've discovered thus far (as have a lot of us married guys), that the trouble with this "solution", is that this process of "talking about it", is never OVER until you've uttered the following words: "Yes dear".
In other words, if you haven't complied with what she wants, and you thus find yourself in a continued tie (impasse), then by definition, you need to "talk about it more". And at no time is the "talking about it" done, until SHE is satisfied with the outcome (lest you simply haven't talked about it ENOUGH).
So I have often found myself enacting what some marriage & fam type counseling/books call "boundries". That's where, instead of coming in and saying something like "can I go to the concert?" (as if it's their say-so to allow you to go or not), you instead come in and say "I'm going to the concert, you're welcome to go if you want". Or in your case, you simply announce "I'm going metal detecting". And when she objects, pouts, and gives you all the reasons why you shouldn't (and instead lists off the things she thinks you should do instead), you listen politely, smile, pause and think, then respond "ok, I've given the matter thought, I've thought through everything you've said, and I've made a decision. I'm still going metal detecting". Very controversial, I know, because it seems to make YOU the "dictator" and takes away the spouses in-put. But CONVERSELY, to think everything has to go through THEIR say-so, simply makes THEM the "dictator", afterall. The "boundries" philosophy was/is more for abuse situations (where women, for example, don't "put their foot down" and let the husband know that a certain activity [vice, cheating, abuse, etc..] must STOP OR ELSE). But I have talked to one marriage/fam counselor friend I know, who said ...... no .. it's not just for abusive situations, but for every situation. Lest otherwise, the partner eventually come to think that all they have to do is wine and gripe, and you'll perpetually cave in, and do exactly as they say. Ie: the "talking about it" isn't over, till you've complied type-thing.
Thought I would be cursed with a permanent pucker lips after that one. She is still 
off over it. 
