An upper for an article of footwear, the upper including a base layer defining a least a portion of the upper and polymer threads stitched to the base layer. The polymer threads may include a core composed of a first material and a coating composed of a second material, where the melting point of the first material is higher than the melting point of the second material. The polymer threads may be bonded to the base layer by the coating of the polymer threads. The polymer threads may include one or more polymer thread sets stitched in pattern(s) on area(s) of an outer surface of the base layer to provide targeted characteristics to area(s) on the upper. In some embodiments, the polymer threads may be bonded to the base layer with heat and/or pressure.