I've seen these particles used in a metaphoric sense, where a fantastic, implausible scenario is presented for effect:
Тебе, наверное, женщины на шею так и вешаются.
Он так и покатился со смеху.
In these cases in English we say The women must literally be throwing themselves at you, or He was literally rolling with laughter. However, I've also seen так и used with plausible situations, but with somewhat "extreme" verbs that describe things the subject is prone to do, yet to a higher, degree:
Дождь так и льёт.
Солнце так и жжёт.
Ветки так и гнулись под тяжестью яблок.
These make perfect sense to me as I assume they mean The rain was absolutely pouring, or *The sun was absolutely sweltering*, or *The branches were literally bending under the weight of the apples*. However, I was hard put to interpret this same "extremeness" in the following sentence.
Кошка так и ластилась к его ногам.
In what situation would somebody say this and what would they mean?