What to look for when purchasing a honing steel?
Magnetizing can cause other problems, especially since you can also end up magnetizing knives which will then be MORE difficult to clean from metal debris.

There are smooth steels which really only set the edge straight; there are properly abrasive ones (diamond, ruby, ceramic), and there is the cheap in-between the ridged steel is. Do not confuse these three. Most criticism of honing steel use is towards ridged steels, combined with careless use.

Use of honing steels is mostly considered a bad idea for harder (60 HRC and above) knives. Especially ridged steels, especially with sloppy/cavalier "kebap cook"/"butcher" style technique. However, a cheap IKEA Santoku, unless it is something VG10 cored, will not be 60 and above. A "good" knife, especially if you choose a japanese style, might very well be. For such, you best use some kind of (paddle) strop for maintenance; a smooth steel or abrasive steel might also work IF used at a proper angle (this means you need the same basic knowledge needed for sharpening freehand on a stone...) and with caution. The "japanese way" appears to be to actually sharpen them on a fine (polishing) whetstone very regularly.

When it comes to abrasive steels, especially diamond!, be aware that you can accidentally change the edge angle significantly, create a coarser edge finish than intended, or raise a burr - all of these are a problem if done unintentionally (and probably inconsistently).