1. Look up the help file for the Pd object to see what it does [in this case, it's a bandpass filter]
2. In Max, choose Help > Max Help. Type a word related to what you found out in #1 into the search box
3. See what comes up. If there's more than one result, look at 'em all. You may meet a new object that way.
4. If nothing comes up, try another phrase related to what you found in #1. Investigate *those* in the hope of meeting new objects.
5. If nothing shows up that way, ask on the Forum.
In your case, it would appear that reson~ or svf would be useful things to check out.
bp~ is indeed a 2-pole bandpass filter, as is reson~, but that does not mean they are remotely similar. if you are porting general Pd patches and just need 'something similar', use reson~ or svf~ or filtercoef~ + biquad~.
"[bp~] only implements feedback sections, not a feed-forward section as [reson~] does; the filtering (peak) is less extreme in [bp~]; it is a lot 'richer', especially when cascading"
so, if you need an exact replica of the sound and response of bp~, i have only come across two max patches that do it (although i am sure there are many more). 1, by volker böhm, using biquad, and 2, by me, using gen~ (which is not technically bp~ as it uses signal rate update, but sounds exactly like it). i tend to use the volker böhm solution. you can find both patches towards the end of this thread: