metronome and audio inserts

There's no automatic tempo detection in any SONAR versions, AFAIK. If you don't know the tempo of the audio, you must either detect the tempo with a third party software, try to find it by little by little changing the project tempo until it matches, or, I think Audio Snap can be used as well, but as I've never used it, I let the more knowledgeable forumites advise you further. I'm sure you'll be given usable info soon.

As the metronome always follows the project tempo, it's the tempo you actually synchronize, not the metronome.

Acidized loops are a different story, as they are more flexible.

Turn on the click, line your audio to start on bar 2, set a starting tempo (insert tempo tap the starting tempo in) , open tempo view (multi dock's a good place), hit play and listen to click, manually draw in new tempos for each bar/beat that needs adjusting (with practice you'll get good). You might have to zoom in or out of the tempo view for finer or courser adjustments. You'll thank yourself for the grid later! Cause then you can enable audio snap and tell the clips to follow project tempo and then RE-adjust your tempo map to YOUR liking with the previously mapped audio following. (DON'T enable audio snap until you're DONE mapping the tempo.)