What is the applicant letter of introduction?
A letter of introduction is just an optional application documents cover letter from the applicant.
If you include one, it should just state:
- visa type applied for
- list of documents included in the application
- any explanations for unusual circumstances surrounding your application, such as unusual activity on your bank account, if you have criminal convictions, if you have any refused visas or entries to the UK in the past.
Also, my biometric appointment is tomorrow and I see that it says to bring all of your supporting documents, so I am going to, but will they actually look at them there? I figure this is more for people applying on a different visa type?
No, actually you shouldn't be taking any of your documents.
Your biometrics is actually done by US immigration at a USCIS office on behalf of UKBA, and it's just a 5-10 minute appointment and has nothing to do with your actual application (your biometrics are just transmitted electronically to UKBA afterwards).
All you need to take is your passport and your biometrics confirmation sheet. They will check your passport, stamp the biometrics sheet, take your fingerprints and photo and then you leave. You put your passport and stamped sheet in your package and mail it to Sheffield to arrive within 14 days.
That information on the email/confirmation is for applicants in all countries - where in some cases you apply in person at a consulate and have to hand in your application to UKBA at your biometrics appointment.
This is not the case in the US, as you mail your application to Sheffield.
I've also come across something on here about a letter from my husband, but I never saw this in all of the documentation I read. What is this and what does it need to say?
This letter is absolutely mandatory, and your visa will be refused without it.
Your husband must write a letter in support of your application, including his employment details, where you will live, a short history of your relationship, and a list of documents he is including with your application.
A sample letter can be found here:
http://www.londonelegance.com/transpondia/sites/default/files/spousal.pdfwhich is from this page:
http://www.londonelegance.com/transpondia/family-visas/spousal-visa (very useful page for spousal visa applications)
Just a note that birth certificates are not required for the application, so you don't need to send them, or copies of them.