Buy the metal tape that is made from heavy gauge metal is usuallt better than the thin metal tape, The thin metal tape is ok to use on flex duct but the heavy tape is much better an IMO has better adhesive. Mastic NO.9 is good to use as well, very easy to apply with a small brush on most typical seams, anything bigger use a good high heat resitive silicone.
I used HVAC mastic on all my joints & seams &holes --
oh yeh, I will bet anyone $100 that they can not remove the 'duct' tape on my pipe joints without scraping without abraiding the stuff away!! applied in 1974, I am sure -- [sure wish I knew what brand & catalogue number!]
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!