A lot of the suggestions so far will work, but use caution. The harsher chemicals will strip paint, dissolve plastic & endanger your health. But generally speaking, if they are not strong acids or abrasive, they won't harm your metal surface. For anything stronger than vegetable oil, I'd wear gloves and clean well afterwords.. you wouldn't want to have chemical residue in your espresso.

The continuum goes something like this..
(nasty) plastic solvents e.g. isopropyl bromide/nitromethane -->carburator cleaner -->dry cleaning solvent -->brake cleaners-->WD40-->canola oil (innocuous)
.

They will all do the job. I have used Goo-Gone, Joe-Glo, WD40, brake cleaner, in a pinch ATF (Automatic Transmission Fluid) will even work. Just about any cleaner will work, even more tape. Pull the sticker off, take a little square of duct tape, stick it on the sticker goo and pull it up. Adhesive sticks to adhesive quite well.

Do you have a source of steam nearby? It works pretty well on many adhesives.

If nothing else works for you, acetone will take it off. Take care since it will dissolve plastics and paint and is explosively flammable, but with adequate ventilation and a bit of care it will work very well.