A spider

[milo]

I was trying iambic pentameter, pretty sure it's all wrong, but a fun attempt, nonetheless.

The sun shines bright upon my window sill,
A spider most pretentiously does crawl,
My mind now screams a spider I must kill!
I grab a nearby lamp intent to maul...
Regrettably my plan now goes astray,
The lamp cord lay in wait across the rug,
I thought I had the spider beat this day,
Piteously, I can only shout Damn Bug!!

pretty close.  You are doing what many do when they first attempt meter which is to twist words into awkward, unnatural positions.  Better to try some different words maybe.  Some examples:

"does crawl"
"intent to maul"
"this day"
"most pretentiously"


You maintain the meter pretty well until the last line.